Welcome to A Traveller’s Guide to Feathers. Visit here for weekly updates on the most exciting recent discoveries from the world of bird biology. Your adventure begins below!
Week 41 – 23 April 2017:
A Tough Time For Dippers
It is now well established that the activities of humans are resulting in significant global climate change. In particular, extreme weather events such as heatwaves, droughts and floods are becoming more severe and more common. How far this change is likely to proceed, and quite how fast, remain to be seen. Wildlife will certainly feel the impact of climate change, but studies of these consequences are needed desperately.
Brown Dippers are almost ideally suited for studies of the impact of extreme flooding. They are found throughout mountainous regions in Japan, Vietnam, Taiwan, China and other parts of central Asia. Pairs establish territories along fast-flowing streams and rivers, and feeds on large, aquatic invertebrate animals that they capture while walking underwater along the streambed. These dippers are comparatively common in places, and are not particularly secretive. They nest on cliff ledges, under bridges, and in cavities.
Shiao-Yu Hong of the National Pingtung University of Science and Technology and his colleagues investigated the impact of extreme flooding events on the reproductive performance of Brown Dippers. Their comprehensive study was conducted in streams of the Tachia River system in central Taiwan between 2003 and 2014. This period saw fifteen flooding events, varying in intensity and lasting from one to three days.
In Taiwan, the typhoon season typically runs from June to October. Hong et al. documented temperature and water flow. Brown Dippers were counted, and reproductive attributes such as laying date and nesting success were recorded. Further, the team sampled the identity and abundance of invertebrate animals in the streams in which the dippers foraged.
Floods resulted in a reduced availability of food for the Brown Dipper, and extreme flooding caused a decline in their survival. More insidious was the impact of flooding on reproduction. The breeding season of these dippers in January to April, several months after the end of the typhoon season. Even so, low food availability following severe floods resulted in later breeding, a lesser number of offspring produced, and a smaller dipper population the following year. For the birds, the most important feature was not the severity of each flood, but the length of time that had passed since the flood had ended. More time allowed the invertebrate animal population to recover.
It is not likely that the Brown Dipper will fall to extinction in the coming decades because of global climate change. However, increases in the frequency and severity of flooding that results from typhoons will almost certainly have negative consequences for them. The results of this study are an important indicator of how changes in climate will influence other wildlife species.
Hong, S.-Y., B. A. Walther, M.-C. Chiu, M.-H. Kuo and Y.-H. Sun. 2016. Length of the recovery period after extreme flooding is more important than flood magnitude in influencing reproductive output of Brown Dippers (Cinclus pallasii) in Taiwan. Condor 118:640-654.
Photo credits: Brown dipper in water, www.chinauniquetour.com; Brown Dipper family, www.pinterest.com
Week 40 – 16 April 2017:
Birds? What Birds?
Scrolling through very old issues of journals devoted to the lives of birds can provide remarkable insight into the ways in which the study of birds has changed. Building on decades of study, research today tends to ask questions that are far more specific than in the past. A century ago, ornithologists were concerned about fundamental aspects of the natural history of birds, rather than minor details of their genetic construction. However, a 1917 issue of the Wilson Bulletin, now known as the Wilson Journal of Ornithology, provides the only article about birds that I have ever come across that doesn’t mention even a single type of bird.
American ornithologist Frank Smith was born in 1857. He was granted a Bachelor of Philosophy degree by Hillsdale College in 1885 and an Artium Magister by Harvard University in 1893. He took up a position at the University of Illinois in Champaign-Urbana, where he was engaged for the remainder of his life. As both a professor in the university’s zoology department and a curator at its natural history museum, he doubtlessly influenced countless young lives.
Smith’s 1917 article in the Wilson Bulletin was, however, something of an oddity. The article’s title promised to demonstrate a link between the weather and spring migratory behaviour of birds. The data set was substantial, having been collected between 1903 and 1916. He explained that birds had been observed in an 18 acre artificial forest, and in Mount Hope Cemetery, immediately adjacent to the university campus. Students in Smith’s ornithology classes, employees of the university, and citizens of the city kept daily records of birds each year between early February and late May.
Smith considered the dates on which bird species were first seen in the spring, referring to them as “firsts.” “The data of “firsts”,” he wrote, “shows a great lack of uniformity of distribution throughout the season. The average season has had 89 days and the number of “firsts” has averaged 120 but these have been so bunched that 61 of them have been recorded on 9 days.” If you understand what any of that means, please tell me.
The days on which bird species were first seen in the spring was compared to daily weather maps of the region. “An examination of the weather maps for the 63 days on which are recorded a half of all the “firsts” of the last 30 days of each of the 14 season shows that on 54 of those days there were approaching areas of low pressure, with south winds which had been effective during the preceding night.” I think that means that southerly winds blow bird north. Smith went on to write that making graphs that compared temperature and wind direction with migratory activity would likely reveal some correlations. Regrettably he didn’t make any.
Let me reassure you that Illinois does, indeed, have birds. In fact 447 species are known from the state, eleven of which have been introduced, and two of which are extinct. Ross’s Geese, Pied-billed Grebes, Northern Harriers and Horned Larks can all be found there. The state bird of Illinois is the Northern Cardinal. You just wouldn’t know any of that from reading Smith’s article.
Smith, F. 1917. The correlation between the migratory flights of birds and certain accompanying meteorlogical (sic) conditions. Wilson Bulletin 29:32-35.
Photo credits: Northern Cardinal – www.pinterest.com; family of Pied-billed grebes, © Rolf Nussbaumer (www.rolfnussbaumer.com) from www.audubon.org
Week 39 – 09 April 2017:
More Discoveries About the Behavioural Ecology of Birds
In the last entry of A Traveller’s Guide to Feathers, I briefly summarized some recent discoveries concerning the behaviour of birds published in an issue of the journal Behavioral Ecology. Of the thirty-nine article in the issue, four were about fish, seven considered mammals, one was about reptiles, and three examined amphibian behaviour. Fully thirteen papers were about birds, demonstrating the importance of birds to our understanding of the world.
Birds of some species are less likely to establish territories close to roads, and several specific causes of this behaviour have been put forward. Matthew Schepers and Darren Proppo (Calvin University, USA) were able to increase the number of territories of six birds in Michigan by playing recorded bird songs near roads. These birds included the Black-throated Green Warbler and the Rose-breasted Grosbeak. These finding may have conservation implications.
Alex Grendelmeier (Swiss Ornithological Institute) and his colleagues also used the playback of recorded songs to investigate bird behaviour. They found that Wood Warblers in northern Switzerland were attracted to a site in which the songs of their species was broadcast. Regrettably some measures of the birds’ breeding biology was reduced at the site with playback, calling into question the value of acoustic attraction in songbird conservation.
Could it be that female birds alter the sex ratio of their chicks, producing more of the sex that suits current conditions? Male Stitchbirds of New Zealand rely on carotenoids to produce brightly-coloured feathers to acquire territories and attract mates. Kirsty MacLeod (University of Cambridge, UK) and her colleagues found that additional carotenoids in the diet of female Stitchbirds did not cause them to lay a greater proportion of eggs that produced sons.
Michelle Hall (University of Melbourne, Australia) and her co-workers studied the territorial responses of male Superb Fairy-wrens to the playback of recorded songs with trills of different lengths. Longer songs are perceived as being more threatening. The researchers were unable to find differences in the reactions of either bold or shy individuals to songs of different threat level.
Some birds, including the Blue-backed Grassquit of South America, perform displays that appear to be both energetically demanding and difficult to complete. Lilian Manica (Universidade de Brasilia) and her colleagues found that the characteristics of the grassquit’s display that require vigour, and those characteristics that require skill, may limit each other, and that signallers of lower quality are particularly impaired.
Alessanra Costanzo (University of Milan, Italy) and her co-workers found that Barn Swallow parents provided more care to chicks that were more darkly-coloured. Dark-colouration was also positively related to the length of telomeres, an attribute of the cell’s chromosomes that indicates high quality. It seems that parent Barn Swallows invested more time and energy to their chicks of highest value.
Within a breeding season, the timing of the onset of reproduction can have significant implications for breeding success. Teresa Catry (Universidade de Lisboa, Portugal) and her colleagues used a long term data set to investigate laying decisions in Lesser Kestrels. They found that individual differences in timing had substantial consequences for reproductive performance, with a significant seasonal decline.
Birds of many species attempt to defend their chicks and eggs against potential predators, and some ground-nesting birds, like the Kentish Plover, are well known for their distraction displays. Miguel Gómez-Serrano and Pascual López-López (University of Valencia, Spain) found that males that displayed greater defence behaviour were likely to mated to females that did the same, and that more defence did result in greater survival of eggs and chicks.
In a laboratory setting, Julie Gibelli and Frédérique Dubois (Université de Montréal, Canada) studied Zebra Finches, quantifying now long it took each bird to forage near a novel object in the vicinity, and challenged individuals with learning tasks. Zebra Finches that were less fearful of new things were also less flexible in their behaviour.
There are many reasons why a researcher might choose to study birds, rather than animals of other sorts. They are comparatively large, not particularly secretive, active during the day, exhibit a wide array of interesting behaviours, and are frequently quite numerous. In the field of behavioural ecology, for instance, we owe much of our understanding of important principles to our study of birds.
Photo credits: Black-throated Green Warbler, © Brian E. Small, www.audubon.org; Kentish Plover, female demonstrating the broken wing display, © Jaysukh Parekh “Suman”, www.orientalbirdimages.org
Week 38 – 02 April 2017:
The Contribution of Birds to our Understanding of the World
The world can be a frustratingly complicated place. Those who choose to go beyond an acceptance of things as they are, and attempt to determine why the world is one way and not another, will always be challenged. Among the natural sciences, physics, chemistry, geology and astronomy are each baffling in their own way, but when it comes to mind-bogglingly difficulty, biology must surely lead the way. Life adds a degree of uncertainty that can drive biologists to the brink of despair. Of all the branches of the biological sciences, the single field that is most likely to leave a biologist staring blankly at a computer screen covered in numbers is behavioural ecology.
Behavioural ecology is an attempt to understand the behaviours of animals on the basis of the evolutionary history of the group and the ecological circumstances of the individual. Why do individuals behave differently when faced with the same challenge? Why does an individual act differently when conditions change?
Many scholarly journals publish the results of research in the field of behavioural ecology. One of the most august of these is the aptly named Behavioral Ecology. It is the journal of the International Society for Behavioral Ecology, and is now in its twenty-eighth year of publication, with six issues each year. The first issue of Volume 28 arrived on my desk recently, composed of thirty-nine research articles over 345 pages.
Here is the curious part. We share the world with millions upon millions of animal species, but there are only 10,000 species of birds. Despite this, fully one-third of all the articles in that issue of Behavioral Ecology were about birds. As with so many other branches of biology, we owe much of our understanding of the world to studies of birds. For instance…
Mathieu Giraudeau (University of Zurich, Switzerland) and his colleagues reported that, at least for Japanese Quail chicks, it is important that quantities of testosterone and carotenoids deposited in the egg by the hen be balanced. Too much of either results in chicks hatching at a lower weight.
According to research by Vittorio Baglione (University of Valladolid, Spain) and his co-workers, parasitic Great Spotted Cuckoos are more likely to lay their eggs in the nests of Carrion Crows than in the nests of Eurasian Magpies in northern Spain, even though magpies were superior hosts. The unexpected result was explained in terms of how well magpie nests were concealed in the two regions.
Birds that are able to occupy both forests and cities face very different physical environments. The reproductive performance of Great Tits in forests and cities in Germany faced differences in temperature, humidity, noise and light, but Philipp Sprau (University of Munich) and his colleagues found that those differences were not sufficient to explain variation in clutch size.
In African widowbirds and bishops, the colour red is known to be important in competition among males for territories. Calum Ninnes (University of Gothenburg, Sweden) and his crew found that by increasing or decreasing the colour red in feathers beyond its natural range, they could increase or decrease the probability that a male Red Bishop would acquire a territory.
In the next entry of A Traveller’s Guide to Feathers, I will summarize additional new understandings about the behavioural ecology of birds.
Photo credits: Japanese Quail – 123RF.com; Red Bishop - © Steve Garvie, https://www.beautyofbirds.com/northernredbishops.html
Week 37 – 26 March 2017:
The Value of Jhum to Birds
To paraphrase Douglas Adams’ description of airports, it can hardly be a coincidence that no language on Earth has ever produced the expression “As pretty as an oil palm plantation.” I have walked through oil palm plantations in southeast Asia, and I have flown over them. On no scale are these plantations anything other than ugly.
And yet in world where a growing human population puts increasing demands on the landscape, monoculture production of plants such as oil palms and teak are seem as an economic saviour. Cutting down native forests and replacing them with these plantations is certain to force out creatures that are committed to live in the forests. Is there a reasonable alternative?
In the north-eastern states of India lie forests that are recognized as global biodiversity hotspots. Traditionally the indigenous tribal people of the region have utilized a system of shifting agriculture known as jhum cultivation. This form of agriculture involves a systematic rotation of land cleared of trees for cultivation, resulting in a mosaic of active and fallow fields, and regenerating and mature forests.
Jaydev Mandal of Gauhati University and Shankar Raman of the Nature Conservation Foundation in Mysore, India, set out to compare the use of mature forests, jhum, and oil palm and teak plantations by forest birds. Their study was conducted in the Dampa Tiger Reserve, the largest protected area in the state of Mizoram. It is a rugged and hilly region. The core of the reserve is free of human settlement, but a number of villages are found around the reserve’s margin. Increasingly the jhum system of cultivation in the area is being replaced by monoculture plantations, with the support of the state government.
Mandal and Raman conducted surveys in March and April of 2014, when the area was occupied by both migrant and resident birds. They recorded over 1300 individuals of 112 species, most of which were forest specialists including the Red-headed Trogon, the Gray-throated Babbler, the Wreathed Hornbill, and the Pale-chinned Blue-flycatcher.
It will surprise no one that oil palm plantations supported the fewest bird species. These plantations have almost no native trees, and are structurally simple. Teak plantations were a bit more useful to birds. Again it is no surprise that the intact native forests had the greatest number of birds of the greatest number of species. “Jhum was thus intermediate between plantations and mature rainforests in habitat structure, bird community composition, and conservation value,” wrote Mandal and Raman.
What does the future look like for birds in north-eastern India? Nothing beats an original intact operating ecosystem, but we live at a time when that is not always an option. Currently the Mizoram State Government’s New Land Use Policy aims to eliminate jhum cultivation, replacing it with other land uses. Given the apparent value of jhum for birds like the Pale-headed Woodpecker and Yellow-vented Flowerpecker, perhaps the state government might help farmers to refine their practices, rather than replace that form of cultivation.
Mandal, J., and T. R. Raman. 2016. Shifting agriculture supports more tropical bird forest birds than oil palm or teak plantations in Mizoram, northeast India. Condor 118:345-359.
Photo credits: Red-headed Trogon, photographed by/© Peter Ericsson (www.pbase.com/peterericsson/profile) – www.phuketbirdwatching.com; Yellow-vented Flowerpecker, photograph/© by wokoti - www.flickr.com/photos/wokoti/4821960569
Week 36 – 19 March 2017:
A Vulture in the Next Life
If I am to be reincarnated, I hope that I will not be brought back as a Cape Vulture. They must have great personalities, because they certainly don’t get dates on the basis of their looks. The scientific name of the Cape Vulture, Gyps coprotheres, is based on Greek words with imply that they hunt dung. They don’t hunt dung, of course, but rather scavenge carcasses of medium and large animals, which doesn’t seem like much of a step up. Even though they nest on cliffs, eggs and chicks are vulnerable to predation by eagles, crows, ravens and baboons. All in all, it sounds like a pretty tough life.
Considered to be endangered by the International Union for the Conservation of Nature, and with a rapidly declining population throughout southern Africa, a group of experts enumerated the forces working against the Cape Vulture. These included inadvertent poisoning of their food, inadequate availability of carrion during the chick-rearing phase, disturbance at their breeding colonies, habitat loss, persecution, electrocution, drowning, lead poisoning, and hunting because of a mistaken perception that eating them will have medicinal or psychological value.
Some experts see the provisioning of Cape Vultures with food at “vulture restaurants” as one of the keys to their survival. The goal is to direct birds away from uncontrolled sources of food, and provide them with predictable, poison-free nutrition. Do these restaurants serve their intended purpose? Studies of other vultures have generally reported a positive outcome. Does this also apply to the provisioning of Cape Vultures?
Dana Schabo and her colleagues recently reported on a twelve-year study of supplementary feeding at a breeding colony of Cape Vultures in KwaZulu-Natal Province in South Africa. Given that an adult pair and their single chick require about 230 kilograms of meat, and that the colony consists of forty-nine breeding pairs and about two dozen non-breeders… well, that quickly adds up to a lot of food. The vulture restaurant has been supplying Cape Vultures since 2001. On the menu are carcasses of cows, pigs and plains zebras, supplied by livestock farmers and a local conservation organization. Feedings varied, depending on the availability of carcasses.
The good news is that supplementary feeding during the nest building part of the year had a positive influence on the number of breeding adults. Schabo et al. felt that additional food permitted adults to enter the breeding season in better condition, allowing them to choose to breed, rather than waiting for conditions to improve. More food, more breeding. Curiously, providing extra food during the incubation and chick-rearing stages did not result in a higher probability of individual breeding success. It could be that not enough food was supplied to meet the needs of a colony full of growing chicks, particularly since the food supply was irregular. Alternatively, the vulture restaurant may have attracted potential predators of vulture eggs and chicks.
When I contacted her, Schabo provided me with further details of the work of the Cape Vulture team. These birds appear to play an important ecological role, but their “scavenging service is completely underappreciated and understudied.” One of the keys to the project was contact with a sugar cane farmer, Mike Neethling. Schabo described him as a passionate bird enthusiast who also happened to have a Cape Vulture breeding colony on his land. Since starting a vulture restaurant more than fifteen years ago, Neethling has made notes on every carcass set out as food, as well as breeding records for the vultures. “Mike is the hero of the story!” wrote Schabo. Because Cape Vultures cannot rip into a carcass by themselves, Neethling goes so far as to cut them open. Watching the resulting frenzy of feeding vultures must be a magnificent sight.
Local vulture enthusiast Andy Ruffle jointed the research team in 2014. He spends endless hours in a hide at the breeding colony, documenting the behaviour of these fascinating birds. Ruffle and Neethling take interested people to the breeding cliffs, detailing the ecological roll of the vultures, and explaining why it is important to protect them.
We will need additional details about the lives of Cape Vultures if we are to be sure of their long-term survival. Since 2012, the research team has been fitting individuals with satellite transmitters to track their movements. The primary focus is young birds because their mortality is so high after leaving the colony. The data is currently being analyzed, and should soon be ready for publication.
You can read more about the important work on these vultures at www.gyps-corotheres.net. Despite the supplemental feedings, I still don’t want to be reincarnated as a Cape Vulture.
Schabo, D. G., et al. 2016. Long-term data indicates that supplementary food enhances the number of breeding pairs in a Cape Vulture Gyps coprotheres colony. Bird Conservation International doi.org/10.1017/S0959270915000350.
Photo credits: Cape Volture perched on “vulture restuarant” sign – www.restafrica.org; Cape Vulture stamp from South Africa – www.pinterest.com
Week 35 – 12 March 2017:
To Feed, Or Not To Feed
Do you provide food for wild birds in your yard? If so, then you are not alone. It seems that nearly half of all householders in Great Britain feed birds, and as many as 53 million households in the United States do the same. Sunflower seeds, nyger, millet, wheat, fat, artificial nectar… it all adds up to an industry worth hundreds of millions of dollars each year. The joy that results when our feathered friends arrive in our yards to feast cannot be overstated. Birds feeders provide opportunities to develop a greater sense of empathy with wild birds. Similarly, there is little doubt that feeding birds in the non-breeding season adds substantially to their over-winter survival.
Despite all of these positive outcomes, is it possible that we are doing more harm than good by feeding wild birds during the breeding season? Could it be that bird feeders create a situation where predation of eggs and chicks increases?
Hugh Hanmer and his colleagues at the University of Reading in the UK addressed this important issue. Rather than struggling with the logistical and ethical challenges associated with predators and real bird nests, they constructed artificial nests from wire mesh, and lined them with dried grass. These were meant to mimic the nests of Eurasian Blackbirds, and were attached to trees at an appropriate height. Each nest received a pair of Japanese Quail eggs. Feeders were installed nearby, either empty, filled with peanuts, or filled with peanuts but fitted with a guard to exclude grey squirrels and large birds such as Eurasian Magpies. Each nest was monitored by a camera that was equipped with a motion-activated trigger.
Of 102 experimental nests, the contents of seventy-four were preyed upon. Those nests that were located close to filled feeders were substantially more likely to have been visited by magpies, squirrels or European Jays, although the difference between predation rates near guarded and unguarded feeders was not statistically significant.
Mark Fellowes, another member of the research team explained to me that the initial idea for the project came to him while watching birds from his kitchen window. ” I have bird feeders in my back garden, and watched a Great Spotted Woodpecker fly from a peanut feeder to a wooden nest box which had a brood of Blue Tit chicks. Within a few minutes it had managed to excavate a new entrance, and then quickly dispatched the chicks.”
“The urban landscape presents a challenging environment for wild birds to live and breed in,” wrote Hanmer et al. Urban dwelling birds may find limited natural foods, and a large number of predators including cats. Despite these challenges, urban environments do support large numbers of wild birds, and the species richness can be high.
To feed, or not to feed? Fellowes’ advice is to continue feeding birds, but to place feeders as far as possible from breeding habitat in the when birds are reproducing. He puts his feeders in front of his house in the breeding season, away from the shrubs and trees used as nesting sites in the back garden. He has also replaced all of his wooden nest-boxes with woodcrete versions to discourage predation by woodpeckers. “I get huge pleasure from feeding birds in my garden,” said Fellowes, “and I want them to benefit from my decisions; I’m pretty sure that everyone who feeds birds feels the same way.”
Hanmer, H. J., R. L. Thomas, and M. D. E. Fellowes. 2016. Provision of supplementary food for wild birds may increase the risk of local nest predation. Ibis 159:158-167.
Photo credits: squirrel-proof feeder – mailshop.co.uk; multi-level feeder – www.amazon.com
Week 34 – 05 March 2017:
One Hundred and Ten Years in the Life of a Chinese Robin
One day you might happen to find yourself travelling on the Northern Line of London’s underground subway system, approaching The Tottenham Court Road station. If someone happens to spill their cappuccino all over your shirt, you could find yourself in need of a new garment. Fear not. You will find a Primark clothing store right across the street from the entrance to the tube station.
That has not always been the case. One hundred and ten years ago, Restaurant Frascati stood where Primark is today. On the 20th of February 1907, forty members of the British Ornithologists’ Club, along with ten guests, gathered at Restaurant Frascati for the 130th meeting of the club. After finishing their dinner and completing the usual business of the club, several members brought out stuffed specimens of some particularly interesting birds. Boyd Alexander displayed six specimens including a male Black-shouldered Nightjar from Africa. Walter Rothschild introduced club members to a stuffed male Dusky-headed Parakeet from Brazil.
Ernst Hartert then brought out a stuffed adult male Rufous-headed Robin, a species that was new to science. The top of its head and the back of its neck were reddish-orange. It had a broad black stripe across its face and around its throat. The rest of the body was varying shades of black, grey and brown. Hartert explained that the specimen had been collected in the Tsin-ling Mountains of northern China, and that three specimens of the species had been deposited in the Natural History Museum’s collection at Tring.
More than a century later, the Rufous-headed Robin remains one of the least-known birds in the world. The International Union for the Conservation of Nature considers the bird to be endangered with a decreasing population. The species has not been observed at the site from which it was first described since its original collection.
When it comes to conservation, that is not sufficient information. Consequently Min Zhao of the Institute of Zoology, Chinese Academy of Sciences, and colleagues endeavored to reveal more about the lives of Rufous-headed Robins, which are found over large parts of Asia. Their findings appeared in a recent publication.
Using DNA from a blood sample collected from an adult male captured in 2015, the team determined that the bird’s closest relative is the widely-distributed Rufous-tailed Robin. Zhao et al. also studied recordings of songs from Rufous-headed Robins, and found them to be most similar to the Ryukyu Robin, a near-threated species from Japan.
In the last twenty-five years, the bird has only been observed in two spots in Sichuan Province. The team considered the habitat and environment of the eight known breeding sites of the Rufous-headed Robin, in the hope that other potential breeding sites of this cryptic species might be revealed. Their modelling suggested that additional breeding sites might be searched for in the mountains of central and northern Sichuan, southern Shaanxi, southern Gansu, and south-eastern parts of Tibet.
We have come a long way since Hartert’s first description of the Rufous-headed Robin. The work of Min Zhao and colleagues revealed new information that may assist in the bird’s long-term conservation. They warned, however, that efforts in China to help this long-distance migrant may not be sufficient. “The fate of the species may depend more on conditions and threats along its migration route and in its wintering quarters.” With only three Rufous-headed Robins ever seen outside of China, two wintering in Malaysia and one migrating through Cambodia, much work remains.
Zhao, M., P. Alström, R. Hu, C. Zhao, Y. Hao, F. Lei, and Y. Qu. 2016. Phylogenetic relationships, song and distribution of the endangered Rufous-headed Robin Larvivora ruficeps. Ibis 159:204-216.
Photo credits: photograph (c) Pete Morris, Birdquest – www.surfbirds.com; painting by John Gerrard Keulemans, from Ibis (1906) – www.wikipedia.com
Week 33 – 26 February 2017:
Scott Johnson in a bird biologist at Towson University in Maryland. About ten years ago, Johnson’s wife, Bonnie, came into the house after watching a pair of House Wrens feeding their newly-hatched chicks in the backyard. Bonnie asked “If only the female incubates, then how does the male know that the eggs have hatched so that he can start bringing food to the young?” Digging through the literature, Johnson found that this brief but crucial period in the reproductive cycle had been the subject of only a single study, conducted half-a-century earlier by the eminent natural historian Alexander Skutch. More investigation was needed.
Johnson and his colleagues have been studying cavity-nesting birds such as House Wrens and Mountain Bluebirds in the central Bighorn Mountains of Wyoming for many years. Long-term investigations of that sort allow researchers to ask more and more sophisticated questions of their study species. For the purposes of these investigations, it is fortunate that wrens and bluebirds are willing to nest in artificial nest boxes. In a recent publication, Johnson et al. addressed the question of how male Mountain Bluebirds know when it is time to begin feeding their chicks.
The team investigated three possible cues for the transition in behaviour. 1. Is it possible that males notice a change in the behaviour of their mates, allowing them to know that the eggs have hatched? Females delivering food, or taking egg shells from the nest could be a good indicator of hatching. 2. Do females produce some sort of visual or acoustic signal to indicate that it is time for the male to be involved? 3. Could it be that a male will only begin to bring food to the nest when he has sensed the newly hatched young for himself? The cue might be the begging vocalizations of the four-to-six new chicks, or the sight or smell of them in the nest.
Johnson et al. used videorecorders to document activity at twenty-four Mountain Bluebird nest boxes. They found no evidence that special displays or vocalizations were given by females. Although some males saw their mates carry eggshells from the nest, or food to it, the researchers found no clear evidence that this was sufficient to cause males to bring food. In all 24 cases, males only began delivering small food items to the nest after they had had the opportunity to sense the chicks for themselves.
Johnson explained to me that one of the most striking features revealed by the research was the incredible variation in behaviour among males. “Some of our males needed but one brief encounter with the nestlings, and perhaps just the sound or smell of them, before they started hauling food back to the nest at a furious pace. Other males entered the next box repeatedly over several hours before the motivation to feed finally kicked in. There are all kinds of potentially intriguing reasons for these differences in male behavior.”
Is this situation the norm in songbirds? Future studies are needed. Additional investigation will also reveal whether a change in a male’s circulating hormones occurs when the transition to feeding begins, and if a male with greater breeding experience makes the transition more quickly.
Johnson described to me his feelings about field work on a high mountain plateau. “The wildflowers are absolutely spectacular. There is abundant wildlife. There were a number of times during the summer that we couldn’t change tapes and batteries in the camera because there was a moose standing near it. I learned a long time ago that you cannot “shoo” a moose… It makes for good stories and, at dinner parties, it certainly makes you appear vastly more interesting than you actually are.”
He is, of course, being far too modest. Field biologists are a pretty interesting group. Be sure to invite one to your next dinner party.
Johnson, L. S., C. L. Connor and A. V. Nguyen. 2016. The discovery of hatching and transition to feeding by male Mountain Bluebirds. J. Field Ornithology 87:384-390.
Photo credits: male Mountain Bluebird – www.pinterest.com; Mountain Bluebirds at a nesting box, photograph by S. and R. Proulx - www.allaboutbirds.org
Week 32 – 19 February 2017:
Small Parasites with Big Consequences
In the previous entry, I described Peregrine Falcons as big, bold and beautiful. Peregrines have been hunted in Europe in the past. The release of hydrocarbons into the environment in decades gone caused eggshell thinning and mortality for both embryos and adults. Despite this, the world population of these wonderful birds now appears to be safe. Even the capture of wild Peregrines on the Arabian Peninsula for use in falconry is having no noticeable influence on their abundance. That is not to say that the life of a Peregrine Falcon is always easy.
Rankin Inlet, a hamlet on the northwestern shore of Hudson Bay in Nunavut, Canada, has about 2500 residents. The region is also home to a dense breeding population of Peregrine Falcons which have been studied intensively since 1982. Starting in 2007, Peregrine nesting sites in the area have been monitored using motion-sensitive cameras. In most seasons, cameras capture the comings and goings of Peregrine parents and their chicks; incubating, brooding, begging, feeding, and so on. The 2013 breeding season was different, as reported by Alastair Franke, principal investigator at the Arctic Raptors Project, and his colleagues.
A pair of Peregrine were in attendance at a monitored nest of four eggs, two of which hatched on 12 July, and the other two a day later. Franke and his team visited the nest on 19 July, and the chicks appeared to be developing normally. When the nest was visited again seven days later, the chicks were gone, and the parents were not in attendance. The nestlings were far too young to have fledged. What had happened?
Images from the cameras revealed the gruesome story. On 20 July, the chicks were being fed and brooded in typical fashion. Footage from 17:15 showed that blood-feeding black flies had descended on the chicks. Within two-and-a-half hours, bleeding lesions could be seen. By 21:00, “all four nestlings displayed widespread, uniformly distributed hemorrhagic lesions over the body and multiple coalescent head lesions.” An hour later, the camera switched to infrared mode, and continued to document events at the nest. Over a thirty minutes period starting at 03:30 the female removed the bodies of all four chicks, now dead, from the nest.
Cameras at other nest sites also showed black fly attacks in 2013. Of ten nests monitored, thirteen of thirty-five chicks died. A less serious outbreak of blood-feeding flies had occurred in 2012, resulting in the death of seven nestlings. In no other year was any Peregrine chick mortality linked to black flies.
Could the deaths of young Peregrines as a result of biting flies be linked to global climate change? Average summer temperatures in the study area have risen by about 1.5 degrees C over the past three decades. Heavy rainfall events have also become more frequent. Franke et al. explained that periodic black fly outbreaks may be nothing more than normal but infrequent events resulting from a particular combination of rainfall and temperature. Either way, it seems that blood-feeding black flies are an important component of the breeding biology of birds in the Arctic.
Franke, A., V. Lamarre, and E. Hedlin. 2016. Rapid nestling mortality in Arctic Peregrine Falcons due to the biting effects of black flies. Artic 69:281-285.
Photo credits: Peregrine Falcon perched on a hotel roof in Manchester city centre - www.rspb.org.uk; nest with chicks - elasharespace2015.wikispaces.com
Week 31 – 12 February 2017:
By anyone’s standards, the Peregrine Falcon is a remarkable bird. They number somewhere between 140,000 and 440,000 individuals, and occupy an area of approximately 387 million square kilometres. There are more than a dozen subspecies of Peregrine Falcon, found in nations from Afghanistan to Zimbabwe, from Moldova to Mozambique. When an individual goes into a hunting stoop, it may achieve speeds of up to 350 km, faster than any other animal. Peregrines are big, bold and beautiful. But sometimes the most interesting details are the tiniest ones.
Consider the delightfully-named Marmaduke Tunstall. A British ornithologist, in 1771 he formally described the Peregrine Falcon for the first time. As part of his description, he gave it the scientific name Falco peregrinus. The first part of the name is straightforward, based on a Latin word for sickle – a reference to its curved talons. The second part of the name is derived from another Latin word meaning stranger or wanderer. According to a dictionary of scientific bird names by James Jobling, this is a reference to a belief in the world of falconry that a young bird captured on its first migration is better suited to the sport than a bird taken from a nest as a youngster.
Falconry continues to be a part of the cultural heritage of people of the Arabian Peninsula, and Peregrine Falcons remain a key species. Traditionally, a falcon would be caught on its southward migration, held during the winter falconry season, and then released so as to avoid the trouble of keeping them through the long, hot summer, as indicated by Tunstall. In Arabia today, falconry uses both wild-caught and captive-bred birds.
A recently-published paper by Aleksandr Sokolov of the Russian Academy of Sciences and his colleagues reported on Peregrines breeding on the Yamal Peninsula of northwestern Siberia, Russia. Falcons breed at low density. Even so, Sokolov et al. documented 59 nesting attempts in 16 breeding ranges between 2008 and 2014. Some of their study involved tracking the movements of birds using satellite transmitter, but some of the work was decidedly less high-tech. Aggressive nest defense of the adult falcons made it possible to get a close look at them. The researchers found that some birds were wearing jesses as used in Arabian falconry. A jess is a short leg-strap made of silk, leather, cotton or nylon. It is used to fasten the falcon to a leash.
The sample size of birds wearing jesses in the study was understandably small, but the stories of individual birds were remarkable. In one case, a female at a nest with four chicks in 2013, and three eggs in 2014, had a blue leg band as well as jesses. The leg band had the telephone number and name of the falconer in Arabic script. When contacted, the falconer indicated that he had captured the bird as an adult on the Red Sea coast of Saudi Arabia in September 2011, but had lost it while hunting about six weeks later.
It is unlikely that the Peregrine Falcons observed in Russia had been intentionally released while still wearing jesses. Like the breeding female described, they were likely escapees. One of the most important messages to come from the research of Sokolov et al. is that these falcons have the potential to breed after a period of use in falconry. The International Union for the Conservation of Nature considers the Peregrine to be of least concern, and with a stable population. In some regions, their populations seem to be increasing. “It appears that the current harvest level of peregrines for Arabian falconry has not prevented breeding population increases and is unlikely to be currently limiting the breeding population… in its northern Eurasian breeding sites.”
Sokolov, A., V. Sokolov, and A. Dixon. 2016. Return to the wild: migratory Peregrine Falcons breeding in Arctic Eurasia following their use in Arabic falconry. J. Raptor Research 50:103-108.
Photo credits: Arab falconer with Peregrine Falcon – www.greenprophet.com; Peregrine Falcon stamp, USSR – www.shutterstock.com
Week 30 – 05 February 2017:
New Truths About Old Birds
The pages of august scholarly journals allow us to know what ornithologists were thinking about 150 years ago. Anyone interested in wading through old copies of such journals will find that bird biology then was very much like bird biology today. Our academic forbears were concerned with the lives of birds, and what caused those lives to be one way and not another. Once in a while, something completely new pops up.
In 1866, a paper appeared in Ibis, the journal of the British Ornithologists’ Union, describing a new species. The author, D. G. Elliot, wrote:
“I am indebted to the kindness of M. Jules Verreaux for the placing in my hands of a new Polyplectron, which in general appearance compares favourably with the handsomest of the known species of the genus. It was sent to the Museum of Paris from Cochin China by M. Germain, after whom I have the great pleasure of naming it.”
Elliot provided the new scientific name, Polyplectron germaini, followed by a very brief description of the bird in Latin, a slightly longer English description of its appearance… and that was all. The report occupied less than a page. Elliot didn’t even reveal what sort of bird it was, assuming, I suppose, that everyone was familiar with the genus Polyplectron. He didn’t have anything to say about the bird’s natural history or abundance. I think the story is worth expanding upon.
The accepted common name for the new bird is Germain’s Peacock-pheasant. Daniel Giraud Elliot (1835 – 1915) was an American zoologist with professional ties to Paris and London. The gentleman who showed Elliot the stuffed bird was Jules Pierre Verreaux (1807 – 1873), a professional collector of natural history artifacts. By 1866 Verreaux had risen to the post of assistant curator of the museum that housed the pheasant, the Muséum national d’Histoire naturelle. The specimen remains in the museum, catalogued as number 1865-577.
The specimen of Germain’s Peacock-pheasant appears to have been collected in Cochinchina, representing the southern third of what is now Vietnam. In 1866 it was a French colony where Louis Rodolphe Germain (1827-1917) served as a veterinary surgeon to France’s colonial army. He probably shot and stuffed birds in his spare time.
This peacock-pheasant is a slightly chunky ground-dweller in Vietnamese forests. Overall it is black and brown, but with numerous large iridescent spots on its back, wings and tail. These spots appear green in some light and blue in others. The beautiful tail is between 22 and 35 cm (9 and 14 inches) long. Females are smaller and a bit duller than males. Its diet is a mystery, and everything we know about its breeding habits comes from birds in captivity.
As far as I can tell, only one additional scholarly paper has ever been published about Germain’s Peacock-pheasant. Destiny Omeire and his colleagues at Texas Southern University and the Houston Museum of Natural Science collected a sample of tissue from a museum specimen. When I asked about the origin of the specimen, Dan Brooks at the HMNS explained that it came from captive stock, rather than from the wild. Omeire and crew extracted genetic material from sub-cellular structures known as mitochondria, determined the complete sequence of the DNA’s constituent parts, and reported their findings in the journal Mitochondrial DNA. The paper’s corresponding author, Hector Miranda, wrote to say that students in his laboratory are sequencing DNA in other peacock-pheasants, and that he is preparing a manuscript “about the phytogeography and pattern of evolution of Polyplectron of Southeast Asia, as driven by climate change since the Pleistocene.”
One hundred and fifty year on, ornithologists are uncovering wonderful new things about birds discovered long ago.
Elliot, D. G. 1866. On a new species of the genus Polyplectron. Ibis 8:56.
Photo credits: Hand-coloured lithograph after Joseph Wolf by J. Smit from Elliot’s ‘A Monograph of the Phasianidae or Family of the Pheasants’ - www.donaldheald.com; Germain’s Peacock Pheasant by Louis Agassiz Fuertes – www.wikimedia.org
Week 29 – 29 January 2017:
I Wonder if Mousebirds Hate Cat Stevens?
Providing for the needs of zoo animals involves much more than a suitable diet, adequate space, and proper veterinary care. Captives require an environment that is enriching. This is particularly true of birds and mammals that may develop behavioural problems in an impoverished environment. Stereotypic acts and self-harm are among the possible outcomes if individuals are not stimulated sufficiently, and in suitable ways.
As a consequence, zoos engage in programs of behavioural enrichment. To date most of these programs have been directed at mammals, particularly primates and carnivores that have particularly complex social behaviours in the wild. Less attention has been paid to the value of enrichment efforts for birds, even though birds and mammals often share the same zoo enclosures.
Recently the Buffalo Zoological Gardens in Buffalo New York studied the value of acoustic enrichment on their captive gorillas. Lindsay Robbins and Susan Margulis of Canisius College in Buffalo took the opportunity to study the responses to enrichment of three species of birds that shared the gorilla exhibit. These were a pair of Lady Ross’s Turacos, two Spectacled Mousebirds, and a Superb Starling. All of these birds are native to Africa.
Over a period of weeks, behaviours of the birds in silent control periods were compared to their behaviours during three acoustic experiences. The first was playback of a compact disk called “Sounds of the African Rainforest.” The second experience involved an assortment of compositions by the classical composer Frédéric Chopin. Finally the birds (and gorillas) were observed during playback of music by the British rock band Muse. That band was chosen because their music contained “no vulgar language or loud, cacophonous sounds.”
Robbins and Margulis documented that nature sounds caused an increase in the amount of flying by members of all three bird species. In terms of flying, the Starling seemed to like Chopin, but none of the birds was keen on Muse. Rock music caused both the starling and mousebirds to vocalize less, but resulted in a significant increase in the performance of vocal duets by the turacos. The researchers concluded that acoustic enrichment of this sort may have a positive benefit on birds held as captives in zoos, without adding substantially to the work load of keepers.
Muses’ 2015 album, Drones, won a Grammy Award for Best Rock Album. They will be headlining at music festivals in Leeds and Reading later this year.
Robbins, L., and S. W. Margulis. 2016. Music for the birds: effects of auditory enrichment on captive bird species. Zoo Biology 35:29-34.
Photo credits: Spectacled Mousebird, photograph © Mike Haworth – howieswildlifeimages.com/2014/11/26/mousebirds/; Lady Ross’s Turacos - www.zoochat.com
Week 28 – 22 January 2017:
From England, to the Sinai, and Beyond
For birds of many species, migration is not optional. In the non-breeding season, conditions on their breeding territories become so extreme that either their needs are not met or their tolerances are exceeded. An English country garden, alive with birdsong in spring is likely to fall silent when winter drives birds south in search of more clement circumstances. Fly away, little feathered friend, or suffer the consequences.
The biggest challenge of migration may not be the journey itself, but the need to find suitable stop-over habitat along the way. If the migratory route is a long one, birds will need to stop for rest and replenishment along the way. Suitable habitat for a short break can be hard to find, particularly if much of the migratory route is over desert.
Andrew Power, Olivia Norfolk and Francis Gilbert of the University of Nottingham in England recently published a paper concerning the value of Bedouin gardens in the southern Sinai to both migratory and resident birds. Power and crew were not in Egypt to just to study birds; the main purpose of their expedition was to collect data on a rare butterfly, the Sinai hairstreak, whose populations are considered to be vulnerable to extinction by the International Union for the Conservation of Nature. Since the researchers were in the region anyway, they took advantage of the opportunity to record their sightings of birds.
The work was completed in the Sinai’s St. Katherine protectorate, essentially a national park, but with added importance. Some birds were noted in the irrigated, managed gardens of the local Bedouin people. Other birds were seen in valley beds and on mountain slopes, habitat which is not managed for agriculture.
In response to an inquiring email message, Power described the circumstances of his field experiences. “I spent long periods of time camping with the Bedouin in the mountains, or in a tourist camp run by the Bedouin.” The camp was very close to St. Catherine’s Monastery, which Power visited several times.
Over a five month period, the research crew documented fifty-one species of birds. Of these, 65% were migrants. Birdlife in the managed gardens was particularly rich. Among the frugivorous birds drawn to the apricots, plums and mulberries of the garden were Golden Orioles and Hooded Wheatears. Garden insects drew in Spotted Flycatchers and Common Redstarts. The gardens were important to resident species too; Collared Doves, Laughing Doves and House Sparrows were seen there, but never in unmanaged habitat. Beyond food and water in the gardens, some bird species utilized Bedouin structures. Power explained to me that Rock Martins and White-crowned Black Wheatears constructed their nests in the walls and on the eaves and sides of houses, taking advantage of almost any crevice.
The St. Katherine protectorate is clearly important for birdlife in the area, and Bedouin gardens, described by Power et al. as “oasis-like,” seem particularly important throughout the year. The Bedouin people collect rainwater to increase the productivity of their mountain gardens, and this action provides much-needed resources for both resident and migratory birds.
A surprisingly large proportion of the migratory bird species that were seen in the Sinai are known to bird enthusiasts in England. If global climate change causes Egypt to become hotter and drier as predicted, the gardens managed by Bedouins may become even more important for wildlife. From the bird’s point of view, it is regrettable that traditional gardening practices are becoming more difficult as Bedouins come to rely more on paid employment. Water is a limited commodity, and tourism and an increasing local population are likely to put further demands on that precious resource.
Power, A., O. Norfolk and F. Gilbert. 2016. The oasis effect: bedouin gardens benefit resident and migratory birds in southern Sinai, Egypt. Sandgrouse 38:7-11.
Photo credits: Dr Andrew Power, https://twitter.com/aerpower?lang=en (set of three photos above) and https://crowcragproductions.com/photos-2/egypt/ (Caspian Tern, below)
Week 27 – 15 January 2017:
Doing the Best With What We Have
Every Sichuan Partridge in China; every Tepui Tinamou in Venezuela; every Chaplin’s Barbet in Zambia… each is ruled by a tiny voice at the back of its head. It is the voice of natural selection, driving it forward. The voice instructs all living creatures to make the maximum possible genetic contribution to following generations. “Reproduce! Reproduce!” cries the tiny voice.
The last 75 years of research has shown that the voice of natural selection is incredibly nuanced. The drive to pass along our genetic legacy is not simply a matter of producing as many offspring as possible, as often as possible. For instance, there is no point in a pair of White-crowned Sparrows producing eight chicks if they can only feed five. A female Welcome Swallow should not produce twelve eggs if all are so small as to be inviable. If a pair of Atlantic Puffins successfully raised three chicks instead of one, but the parents died from exhaustion at the end of the breeding season, the tiny voice would likely be displeased.
In their attempt to pass along their genes, all creatures are faced with tradeoffs. Some of these tradeoffs were illustrated neatly in a recently-published study of Yellow-billed Gulls in northern Africa by Addessalem Hammouda and his colleagues. They observed the reproductive efforts of the gulls at a colony on the Mediterranean coast of Tunisia. At 131 nests, Hammouda et al. noted the days on which each egg was laid, the volume of each egg, and its fate.
The majority of Yellow-billed Gulls at this colony had a three-egg clutch, with a lesser number producing two eggs. The volume of these eggs varied considerably from 61 to 107 ml (2.1 to 3.6 ounces). Hammounda and his team found that the last-laid egg in the clutch was likely to be the smallest. They also discovered that the volume of eggs in three-egg clutches tended to be larger than those in two-egg clutches. Over the 27-day incubation period, 92% of all eggs hatched successfully, but that success was higher among three-egg clutches. What does it all mean?
In the Yellow-billed Gull, last-laid eggs tend to produce the last-hatched chicks. When food is scarce, the slightly-younger, slightly-smaller chicks tends to be outcompeted by their siblings. It seems as though females are investing more resources in their first eggs because those are likely to produce chicks with a higher probability of surviving.
Creating eggs is almost certainly demanding for female birds. It seems that the female gulls that are sufficiently robust to lay three eggs are also in sufficiently good condition to create larger eggs. Females who are able to create three large eggs are also better able to defend those eggs against predation than females producing two smaller eggs. Curiously, terrestrial predators such as snakes and rodents were very rarely seen in the vicinity of the gull colony. However, predation of eggs by other Yellow-billed Gulls was seen frequently.
Although the birds in the Tunisian study were not marked for individual identification, and so the ages of individuals were not known, it is likely that age plays a role in reproductive tradeoffs. Older, more experienced birds are likely better able to acquire resources and defend their nests than younger birds. Beyond that, an individual that is approaching the end of its life may hear the little voice say: “What are you waiting for? This could be your last chance!” Hammouda et al. explained that older females are “likely to have lower residual reproductive potential,” and so should “invest more heavily in current breeding attempts.”
The little voice is subtle, but it is also relentless.
Hammouda, A., F. Hamza, J. Pearce-Duvet and S. Selmi. 2016. Relationship between clutch size, egg volume and hatching success in a Yellow-billed Gull Larus michahellis colony in south-eastern Tunisia. Ostrich 87:139-144.
Photo credits: Yellow-billed Gull stamp - birds-on-stamps.com; photograph of Yellow-billed Gulls by Cosmin-Ovidiu Manci - birds.nature4stock.com
Week 26 – 08 January 2017:
A Celebration of Good News
In 1908, a writer named Minori Ogawa published an article in the scholarly journal Annotationes Zoologicae Japonenses. The paper described birds from the southern islands of Japan. It seems that a Mr. Alan Owston of Yokohama had employed two men to shoot birds to add to his burgeoning collection of stuffed specimens. Between May and December of 1904 the collectors gathered specimens of 124 bird species.
According to Ogawa’s article, the collection included a thrush previously unknown to science. Ogawa described the Amami Thrush as being similar to White’s Thrush, but with twelve tail feathers instead of fourteen, and with a thicker, longer and darker bill. Ten specimens of this thrush were added to Owston’s collection. The bird was, and still is, known only from a single island, Amami-Oshima.
Leap forward a century…
The Amami Thrush, now considered to be a subspecies of the Eurasian Scaly Thrush, was doing very poorly. In 1996 the estimate of its abundance was just 58 individuals. Found on just a single island, the habitat favored by the Amami Thrush, old-growth broad-leafed forests, had been subject to clear-cut harvest between the late 1950s and 1970s. Far fewer trees meant far fewer thrushes.
And if that weren’t bad enough, thirty small Indian mongoose had been released on Amami-Oshima in 1979 in hopes that they would control populations of a venomous snake. In twenty years, the mongoose population grew from thirty to over 6,000 individuals. If you were a hungry mongoose, would you rather tackle a deadly venomous pit viper or a harmless little thrush?
Now comes the good news, courtesy of a recently published paper by Taku Mizuta and his colleagues. As a result of an eradication program that began in the year 2000, the population of mongooses has been significantly reduced. When contacted, Mizuta explained to me that it was likely that the last mongooses would be eliminated from Amami-Oshima by 2023. The large-scale clearance of mature forests on the island has declined since the 1970s, and it appears that habitat suitable for Amami Thrushes may be recovering. Have the birds responded to the change in circumstance?
Among the difficulties of assessing the abundance of these forest-dwelling thrushes is their timidity. It is simply a hard bird to spot. Fortunately, male Amami Thrushes have a loud, distinctive and melodious voice. Dedicated members of the Amami Ornithologists’ Club have, year after year, been engaged in formal censuses of their thrush. Starting before sunrise, they have been walking transect lines, listening for the thrush’s song, and plotting their observations on maps. In other areas, club members stood in particular spots for 50 minutes, documenting all of the Amami Thrushes heard.
Mizuta and his colleagues described the results of these surveys. They worked from the reasonable assumption that only adult male Amami Thrushes sing, and that females and immature males do not. They concluded that the thrush population has now climbed to about 5,000 males and females capable of breeding. Formally thought to be critically-endangered, as a result of the efforts of members of the Amami Ornithologist’s Club we can now say that the population is at least stable or may still be increasing.
Mizuta et al. wrote: “We intend to continue this public-participation survey for many years as a means of promoting further conservation of the Amami Thrush.” Has awareness of the plight of the bird increased? Mizuta wrote to me to say that the local newspaper and radio station have been reporting the results of the surveys each year, allowing locals to better identify with the birds. The social situation also seems to be changing for the better. The Japanese government is applying to have the Amami and Ryukyu islands added to UNESCOs list of World Heritage sites, and locals are showing more interest in the natural history of their part of the world.
All of that seems to be worth celebrating.
Mizuta, T., et al. 2016. Song-count surveys and population estimates reveal the recovery of the endangered Amami Thrush Zoothera dauma major, which is endemic to Amami-Oshima Island in south-western Japan.
Photo credits: Scaly thrush - zipcodezoo.com/index.php/Zoothera_dauma; Scaly thrush stamp – colnect.net
Week 25 – 01 January 2017:
Seabirds Improve the Lives of… What Did You Say?
Forgive yourself if you have never heard of tardigrades; most people haven’t. Also known by the common names “water bears” and “moss piglets,” chances are very high that you are currently sitting just a few metres from members of one or more species of tardigrade. Even so, the probability that you will ever see a tardigrade is vanishingly small.
Tardigrades themselves are vanishingly small; most species are invisible with anything less than a very high quality microscope. You can’t eat them, and they can’t eat you. They don’t spread diseases, nor do they have any marketable qualities. Researchers have described about 1200 species of tardigrades, and it is entirely possible that you will never hear the word “tardigrade” ever again. But that doesn’t mean that they aren’t interesting to bird enthusiasts.
Little Auks (Alle alle) are, as their name implies, small seabirds. They eat plankton, and breed colonially in the high Arctic. They are among the most abundant seabirds in the world, and so despite their diminutive size, Little Auks have the potential to greatly modify the local environment around their colonies. As with other breeding seabirds, some of the nutrients they extract from the sea are defecated over land, changing the chemistry of the soil.
Spitsbergen Island is tucked neatly between the Arctic Ocean and the Greenland Sea, and is administered by Norway. A Polish research station has been operating at Hornsund, a fjord on southern Spitsbergen, for nearly sixty years. In 2016, Krzysztof Zawierucha of Adam Mickiewicz University in Poznań and his colleagues reported on a study of the impact of breeding Little Auks on the tardigrade community of Hornsund.
Zawierucha and his team collected moss and lichen along two transects, each a kilometre-long. One of these transects stretched from a colony of 30,000 Little Auks down to the sea. A second transect, not influenced by the Little Auk colony, acted as a control. Could it be that the enrichment of the soil downhill from the seabird colony resulted in more tardigrades? Might the species composition of the two sites be different?
Peering through their microscopes, Zawierucha and company found 1990 tardigrades from 32 different taxonomic groups with enchanting names like Isohypsibius elegans and Microhypsibius bertolaniii. Tardigrades were more abundant in the vicinity of the Little Auk colony than in the region not influenced by the seabirds, making this report the first to find a positive effect of seabird faeces on tardigrades in a polar region. Zawierucha et al. concluded that fertilization of the soil by the seabirds enhanced plant growth, which created small-scale climates that were more favorable for tardigrades.
Representatives of fifteen tardigrade taxonomic groups were found in both situations, but ten were found only along the control transect, and seven were found only along the transect leading from the Little Auk colony. Some of the differences might be attributable to small-scale differences in the environment, such as greater acidity of the soil downhill from the seabird colony. Some of the tardigrade species collected in this study had never been recorded in the region before, illustrating our lack of knowledge about many aspects of polar biology.
When I contacted Zawierucha, he explained that his main research interest was tardigrades, concerning himself with their ecology, taxonomy and biogeography, but that he was very fond of other invertebrate groups as well. He is interested in glaciers and creatures that live on glaciers as models for life that may exist on other planets. “When I saw glaciers for the first time,” he wrote, “I realised that they define rules of biodiversity and isolation.” Whether it is seabirds or miniscule animals that few people have heard of, field biologists have no end of exciting research ahead of them.
Zawierucha, K., K. Zmudczyńska-Skaarbek, Ł. Kaczmarek, and K. Wojczulanis-Jabukas. 2016. The influence of a seabird colony on the abundance and species composition of water bears (Tardigrada) in Horsund (Spitsbergen, Artic). Polar Biology 39:713-723.
Photo credits: light micrograph of a tardigrade, photograph © Sinclair Stammers – www.extremetech.com/extreme/218492-tardigrades-already-impossible-to-kill-also-have-foreign-dna; Little Auk - www.newhorizonsonline.co.uk/gallery-items/little-auk/
Week 24 – 25 December 2016:
Things We Know and Things We Don’t
Birds are, without a doubt, the best known creatures in the world. Most are brightly-coloured, reasonably large and abundant, display interesting behaviours, and are particularly active during the day. Consequently birdwatching is a hobby; wormwatching isn’t. Birds have been under scientific scrutiny for centuries, and much of what we know about the natural history of animals in general is based on what we first learned about birds.
Some bird species are much better studied than others of course. Thousands of scholarly publications have considered the lives of Mallards and Barn Swallows, partly because they are both common species found in places with lots of people to watch them. At the other end are Black-browed Babblers and Cayenne Nightjars about which we know almost nothing, particularly because they are extraordinarily rare. They reside in countries with very few bird biologists, and may have already fallen to extinction.
In terms of our knowledge of natural history, most species of birds fall somewhere in the middle. They are reasonably common and we know quite a bit about them. There are, however, exceptions.
The International Union for the Conservation of Nature considers the Stripe-cheeked Woodpecker, Piculus callopterus, to be of least conservation concern. A species endemic to Panama, they are not wildly common and have a patchy distribution, but at least their numbers seem stable. So why is it that we know so little about them? In part the answer is that the forests of the foothills of eastern Panama are very difficult to access.
Until recently no one had ever reported seeing the nest of one of these Panamanian woodpeckers. A 2015 publication by William Adsett and Leslie Lieurance changed all of that. In April and May of 2013, Adsett and Lieurance had the great fortune to observe the comings and goings of a pair of Stripe-cheeked Woodpeckers attempting to raise chicks in forest in Chagres National Park in the foothills of eastern Panama.
By great fortune, the pair of birds choose to excavate a nesting cavity in a Cecropia tree very close to Adsett’s home. When I contacted him, Adsett explained that he and his wife own a property within the Altos de Cerro Azul, a residential development of 2000 lots within Chagres National Park. This region represents one of the highest and wettest parts of the entire watershed of the Panama Canal. “We are fortunate in having the Stripe-cheeked Woodpecker frequently in our bit of the forest,” Adsett explained, “but it was sheer luck that the pair nested in sight of our house.”
A combination of direct observation and time-lapse video footage provided Adsett and Lieurance with our first insights into the private lives of breeding Stripe-cheeked Woodpeckers. For instance, the opening to the nesting cavity was 3.4 metres (11 feet) from the ground where the tree was 20 centimeters (8 inches) in diameter. It took nine or ten days from the start of excavation until the first egg was laid, and incubation lasted 12 or 13 days. Both parents incubated the eggs and fed the young, but it was the male that made the greatest number of feeding trips and spent each night in the nesting cavity.
I wish that I could report a happy ending, but I can’t. The young woodpeckers died 17 or 18 days after hatching, which was about a week before they might have been expected to leave the nest. Although they could not be certain, Adsett and Lieurance felt that failure was likely attributable to predation. A large column of army ants was observed to enter the nest, but whether they were responsible for the death of the chicks is unknown. It is possible that a nocturnal predator took the nestling, either dead or alive, after the ant attack.
“It is our guess that this species do not generally return to the same nest hole for a second or third attempt – the trunks just deteriorate too fast.” Adsett explained that cavity-nesting in the tropics can be a precarious business. The excavation of a different nest in a dead tree by the same species caused the trunk to snap off just days after completing the hole.
Adsett, W. J. and L. Lieurance. 2015. First breeding record, vocalisations and morphology of Stripe-backed Woodpecker Piculus callopterus, a Panamanian endemic. Cotinga 37:79-86.
Photo credits: Stripe-cheeked Woodpecker, © Paul Jones – www.flickr.com/photos/paulbjones/24765456272; drawing of a Stripe-cheeked Woodpecker - www.hbw.com/species/stripe-cheeked-woodpecker-piculus-callopterus
Week 23 – 18 December 2016:
The Lives of Birds are Rarely Simple
In eighteen century Europe, when songbirds disappeared from their breeding grounds in autumn, it was hard for many people to believe that they flew thousands of kilometres to spend the winter in more clement regions. Some eminent naturalists imagined that small birds such as swallows burrowed into the mud at the bottoms of rivers and lakes in autumn, only to emerge unharmed in the spring.
Even after centuries of study, many aspects of the migratory behaviour of birds remain a mystery. It is that mystery that makes migration a rich field of study, open to both high-tech and low-tech approaches.
A recent publication by Andrea Harnos and her colleagues at Szent István University, the Hungarian Natural History Museum, and Eötvös Loránd University, all in Budapest, revealed the wealth of information that can result from a low-tech approach to the study of migration. Their report described the result of a study of the small European Pied Flycatcher between 1989 and 2014 as the birds migrated between breeding grounds in Europe and wintering areas in Africa. For 26 years, volunteers erected nets, captured flycatchers, measured them, and documented their age and sex before sending them on their way. The study was conducted in Danube-Ipoly National Park in central Hungary.
Over a period of 26 years, data was collected for 2323 Pied Flycatchers. Among the discoveries of Harnos et al. was that males on their spring migration passed through the study area 11 days earlier in 2014 than they had in 1989, but that females had not changed the timing of their northward migration. No significant changes occurred in the timing of autumnal migration by either sex over the course of the study.
The wings of spring migrants averaged 2 mm longer at the end of the study, and earlier migrants had significantly longer wings than birds who passed through the study area later in the season. In contrast, the wing length of autumn migrants did not change over the study, and earlier arrivals had shorter wings. Of spring migrants, 60% were male, but females accounted for 61% of autumn migrants.
At first glance, this might seem like a confusing collection of results, but Harnos and her colleagues believe that they have untangled the story. In terms of timing, males that arrive on the breeding grounds earlier gain an advantage over later males in terms of attracting a mate; climate warming has likely allowed their average migration dates to shift to earlier dates. For some reason females did not complete their northward migration earlier, so neither breeding nor southward migration could happen earlier.
Other findings are also likely to be related to climate change. Pied Flycatchers have a vast breeding distribution in Europe and Asia, and populations differ slightly in body size. Changes to climate have likely caused shifts in the migration routes of many bird species, such that the research group in Hungary were probably capturing Pied Flycatchers from different populations at the beginning and end of the study. Differences in sex ratio between spring and autumn probably reflects the complex nature of migration, with male and female flycatchers taking different routes between breeding and overwintering grounds.
Anyone seeking simple answers should probably avoid the field of avian migratory behaviour. Even so, you can rest assured that songbirds do not spend the winter underwater.
Harnos, A., Z. Lang, P. Fehérvári and T. Csörgő. 2015. Sex and age dependent migration phenology of the Pied Flycatcher in a stopover site in the Carpathian Basin. Ornis Hungarica 23:10-19.
Photo credits: male Pied Flycatcher – drawing of male Pied Flycatcher - www.rspb.org.uk/birds-and-wildlife/bird-and-wildlife-guides/bird-a-z/p/piedflycatcher/; photo by Rob Vaasse, The Netherlands, May 2003, www.birdforum.net/opus/European_Pied_Flycatcher
Week 22 – 11 December 2016:
Silly Bird, Smart Bird
Hornbills are ridiculous. Just look at them. They are among the silliest-looking creatures ever. Outrageous they may be, but they are not dimwitted when it comes to solving the challenges of life.
There is a fundamental principle in community ecology that states that perfect competitors cannot coexist. If members of two species attempt to exploit the same essential, limited resource in the same place at the same time in the same way, one will be eliminated. This ecological principle is so entrenched in the discipline that it even has a name – competitive exclusion.
How then do three species of large hornbills, all doing essentially the same thing with their lives, manage to co-exist in the tropical forests of far-northeastern India? Rohit Naniwadekar of Manipal University, Charudutt Mishra and Aparajita Datta of the Nature Conservation Foundation in Karnataka set out to discover how these hornbills exploit limited food resources in slightly different ways, allowing them to occupy the same regions at the same time. This was part of Naniwadekar’s Ph.D. study.
The three bird species under consideration were the Great Hornbill (considered by the IUCN to be near-threatened), Wreathed Hornbill (of least conservation concern), and the Rufous-necked Hornbill (vulnerable to extinction). The study was conducted over a period of more than two years in the Namdapha Tiger Reserve in Arunachal Pradesh. In what ways did these birds differ in the way that they exploited fruit in forest trees?
After tramping endless kilometres along forest trails, Namiwadekar and his coworkers found subtle differences in the diet and behaviours of the hornbills that allowed them to defeat competitive exclusion. Although all three species had a varied fruit diet, Great Hornbills spent much more time dining on figs than they did on non-fig fruits. Upon finding a suitable fig tree, they spent an average of 21 minutes feeding there before moving on. Wreathed and Rufous-necked hornbills spent a greater proportion of their time foraging from non-fig fruit trees, where they averaged 43 minutes and 10 minutes respectively.
Wreathed and Rufous-necked hornbills behaved differently in their search for food, allowing them to both exploit non-fig fruit trees. Wreathed Hornbills travelled long distances in search of fruit, which was energetically costly but provided abundant opportunity to find areas with the highest fruit availability. In contrast, Rufous-necked Hornbills were more sedentary, and kept themselves well informed about the availability of fruit over a much smaller home range. Even though they had similar diets, Wreathed and Rufous-necked Hornbills employed different solutions to the trade-off between travel costs and foraging efficiency.
Given that these species have somewhat different diets, and exploit food resources in different ways, Naniwadekar et al. concluded that: “the three sympatric hornbills play a complementary role in seed dispersal.”
When I contacted her about the hornbill study, Datta explained that it is necessary to follow the birds for long periods in order to understand some aspects of their behaviour; this is particularly difficult in dense tropical forests. Hornbills “are wary of people due to hunting in most areas… There are often physical and logistical challenges working in remote tropical forests, where research is mostly on foot, heavy rains often disrupt work, malaria is common, while leeches and ticks… are also common.
Of the hornbills the group studied, the Rufous-necked is in the greatest peril. They have been extirpated from Nepal, and have a very restricted distribution in India. They may be found at altitudes as high as 2000 metres. Most regrettably, many of the forests at higher elevations are not legally protected, and the Rufous-necked Hornbill is hunted by some of the tribal communities for their beaks and feathers. Studies like the one by Naniwadekar and his colleagues will provide insights into hornbill biology that could have implications for their conservation.
Naniwadekar, R., C. Mishra and A. Datta. 2015. Fruit resource tracking by hornbill species at multiple scales in a tropical forest in India. Journal of Tropical Ecology 31:477-490.
Photo credits: Rufous-necked and Wreathed Hornbills - orientalbirdimages.org (Rufous-necked Hornbill (c) Ateeb Hussain; Wreathed Hornbill (c) Wong Tsu Shi); Great Hornbill – Pinterest
Week 21 – 04 December 2016:
A Bird Too Beautiful
Physics, chemistry and astronomy are simple. Each of these disciplines is governed by a limited number of physical laws. If the chemical naphthalene melts at 80.2 degrees Celsius today, it will melt at 80.2 degrees Celsius tomorrow. If Mars takes 24 hours, 37 minutes and 22 seconds to rotate on its axis this week, the same will be true next week.
Biology is difficult. At every turn, life introduces uncertainty, meaning that if 1435 Pied Wagtails show up at a nocturnal roost in Scotland tonight, we cannot know with absolute certainty how many will show up tomorrow night. When biology become conservation biology, the world becomes a ridiculously complicated place. Every conservation issue involves a tangle of interactions among countless species, interactions between those species and their non-living world, and complications of economics, ethics and politics.
Surely there is no place in the world where conservation biology is more complex than China. Considering birds alone, the nation has almost 1400 species, seventy-five of which breed in China and nowhere else. Among China’s endemic birds, the Sichuan Partridge, Hainan Peacock-pheasant, Silver Oriole and Blue-crowned Laughingthrush are all endangered and declining in number. The Manchurian Reed-warbler, Grey-hooded Parrotbill, Cabot’s Tragopan and many more are considered vulnerable.
Chunfa Zhou and Zhengwang Zhang of Beijing Normal University and Jiliang Xu of Beijing Forest University recognized the need for up-to-date information on the abundance and distribution of Reeves’s Pheasant. Endemic to central China, this pheasant was, comparatively recently, abundant and distributed widely. As a result of illegal hunting and habitat destruction and fragmentation, Reeves’s Pheasant is currently recognized to be Vulnerable by the IUCN. Zhou and her colleagues asked if that category was appropriate.
In the search for the pheasant, field surveys were supplemented by interviews of local residents, elders, village heads and hunters, and with personnel in county forestry bureaus. Sightings of birds along transect lines, the sound of the pheasant’s “wing-whirring displays,” and the presence of moulted feathers were all used as evidence of ongoing occupation of an area.
The results of Zhou et al. were not encouraging. Since earlier surveys, 46% of sites had lost their Reeves’s Pheasants, and many other populations had declined in abundance. The human population continues to grow in the area, and economic development plans are likely to make the situation worse in the future.
Zhou et al. wrote: “The long tail feathers of the male Reeves’s pheasant are widely used for decoration of Chinese opera costumes… and consequently a great number of Reeves’s pheasants are hunted.” These birds may be too attractive for their own good. Poaching was apparent at 83% of surveyed sites, and poisoning at 20% of sites. “Farmers in China deliberately poison Galliformes (grouse, pheasants etc.) to prevent them from eating crop seeds,” wrote Zhou et al. In rural areas, it seemed that people were not conversant with national policies on wildlife, and conservation education programs directed at small towns did not get the message to those in remote rural situations. The booming Chinese economy has led to ongoing deforestation of the exactly the sort of habitat preferred by Reeves’s Pheasant.
As the Chinese government works to upgrade its conservation policies, it is important that the best estimates of abundance and distribution be considered. Zhou and her colleagues suggested that the status of Reeves’s Pheasant be upgraded to a first-grade nationally protected species, and that the IUCN change the bird’s status from vulnerable to endangered.
Zhou, C., J. Xu and Z. Zhang. 2015. Dramatic decline of the vulnerable Reeves’s Pheasant Syrmaticus reevesii, endemic to central China.
Photo credits: Reeve’s Pheasant - www.tumblr.com; Reeve’s Pheasant stamp - sandaproject.blogspot.com.au
Week 20 – 27 November 2016:
Then and Now
Many fields of scientific endeavour have changed dramatically in my lifetime. New technologies have allowed great advances in astronomy, physics, chemistry, and some branches of biology. Ornithology less so. I think the reason is that biologists studying birds acquired most of the tools that they needed early on. Binoculars, a notebook and pencil, a rain jacket and hat… What else do you need?
It is true that our capacity to track individual birds has increased greatly as a result of advances in transmitter technology, but many studies continue to use nothing more sophisticated than numbered aluminum leg bands. Progress in gene sequencing has allowed us to leap forward in our understanding of evolutionary relationships among birds groups, but ornithologists still return to museum collections to measure stuffed specimens.
If we go further back in the history of ornithology, differences between then-and-now become more apparent. Papers concerning bird biology published a century ago were far less numerical than they are today, and statistical analysis of data was rare. It also seems to me that research then was less likely to be directed at answering fundamental questions.
For more than 130 years, The Auk has been one of the three great journals dedicated to research on birds. In the January 1916 issue was an article by Henry J. Fry concerning seasonal declines in birdsong. The study was conducted at the field station at Cold Spring Harbor, Long Island, New York. Although Fry was not absolutely clear, it seems that he was teaching a course in ornithology at Cold Spring, and had his students collect observations. The songs of birds were noted each day between 06:00 and 07:30, and between 10:00 and 11:30, in addition to alternating afternoons. The study ran from July 1 to 10 August.
One by one, Fry described the lessening of singing by birds as the season progressed. “The Scarlet Tanager (Piranga erythromelas)” wrote Fry, “was in full rich song till about July 16, though further study may show this day to be inaccurate by several days. From that time on the song declined steadily and the last one was recorded on the twenty-seventh.”
“The Wood Pewee (Myiochanes virens) began its decline almost imperceptibly around July 20, and from that day it gradually became less and less, though the daily diminution was scarcely evident.” And that was that. Fry did not speculate about the cause of seasonal variation in the volume and frequency of singing, nor about possible reasons for species’ differences in behaviour. It wasn’t science. At best it was natural history.
But consider this… It appears that global climate change may be causing some birds to alter their behaviour, such that they breed earlier in the year. In 1914 Henry Fry generated a systematic data set of the singing behaviour of more than two dozen species of birds. In doing so, he created an opportunity. A dedicated student of birds could reproduce Fry’s study to look for changes more than 100 years later. The Cold Spring Harbor Laboratory is still there to facilitate study.
My efforts to find out more about the life of Henry Fry have resulted in little success. He may have been at Columbia University in some capacity in the 1890s. He appears to have been an associate member of both the American Ornithologists’ Union and the Delaware Valley Ornithological Club at the time he wrote his paper on singing behaviour. He may eventually be commemorated by a student keen to replicate his work. Are there any takers?
Fry, H. J. 1916. A study of the seasonal decline of bird song. Auk 33:28-40.
Photo credits: Scarlet Tanager stamp - colnect.com; Wood Pewee – www.birdfreak.com
Week 19 – 20 November 2016:
When Bigger is Better
The differences in nest architecture among bird species are remarkable. At one end are the nests of Killdeer, constituting no more than a few bits of gravel scraped into a circle around a slight depression in the ground. At the other end are the gigantic nests of some raptors that grow in size with the passing years as the resident pair adds more and more material.
As with so many things in life, nests represent a tradeoff for the birds constructing them. More time and effort spent on building the perfect nest might result in better survival of the eggs and chicks, but this could come at the expense of time not spent in self-maintenance and foraging. Biologists are interested in how individuals resolve such tradeoffs. What is the optimal solution? Which alternative will result in the greatest lifetime reproductive success?
Michał Glądalski and his colleagues at University of Łódź in Poland are involved in a long-term study of birds utilizing artificial wooden boxes for nesting. Since 2012, Glądalski and his crew have been studying Great and Blue tits nesting in boxes in two habitats in central Poland. A mature deciduous forest contains 300 nest boxes, while a parkland site with fragmented tree cover has 200 boxes. To these nest boxes, tits add moss and dry grass to complete an outer structural component, and hair and feathers as an inner lining. As measures of reproductive success, the number of eggs in the nest, the proportion of eggs that hatched, and the proportion of hatchlings that eventually fledged from the nest were all documented.
Compared to most songbirds, tits lay a lot of eggs. The average clutch size of Blue Tits varied between ten and thirteen; Great Tit clutch sizes averaged between eight and eleven. Nests constructed within boxes by Blue Tits were considerably larger and heavier than those of Great Tits. Nests did not differ significantly between the two habitat types.
The key finding of the study was that, in general, the greater the mass of the nest lining, the greater the reproductive performance of the parents. Overall nest size and mass was also important. In tits, the nest serves to help maintain an optimal warm and humid environment for the eggs and young nestlings. Where nests are concerned, bigger appears to be better.
Or so it would seem. Studies to date have not fully disentangled the relationship. Nests characteristics alone may not explain everything. It is possible that parents that are more experienced or in better physical condition are able to construct better nests, but are also better able to care for their eggs and chicks. Is nest size the crucial factor, or is it the effort made by the parents? “Future experimental studies… should at least try to efficiently separate these two factors,” wrote Glądalski et al.
It is possible for a researcher to become so focused one particular aspect of their topic that the “bigger picture” is lost. Glądalski and his team are considering the lives of birds utilizing nest boxes in Poland from many different perspectives. When I contacted him, Glądalski explained that he and members of his group are considering breeding success, physiological stress, the influences of heavy metals, variation in egg size, and the genetics of individuals in their population. Glądalski is particularly interested in the ways that global climate change might influence the timing of reproduction and nest characteristics. I suspect that this sort of comprehensive approach is likely to result in a more profound understanding of bird biology in the long term.
Glądalski, M., et al. 2016. Effects of nest characteristics on reproductive performance in Blue Tits Cyanistes caeruleus and Great Tits Parus major. Avian Biology Research 9:37-43.
Photo credits: Blue tit coaxing a chick to fledge, photo by Andrew Williams - www.bbc.co.uk/nature/21445671; Great tit and chicks - www.audubon.org/news/build-nest-box-welcome-spring-birds
Week 18 – 13 November 2016:
Did I Just Hear An Explosion?
In an environmental sense, a catastrophe is a sudden and violent change, unpredictable and experienced infrequently, but resulting in widespread damage. Earthquakes, cyclones, tsunamis, cataclysmic floods and wildfires create such rapid changes in the physical environment as to challenge the ability of plants and animals to respond. Should I stay, or should I flee?
With the eruption of the Puyehue volcano in northwestern Patagonia on June 4 2011, Pablo Alarcón of the National University of Comahue in Argentina and his colleagues were handed a unique opportunity to study the responses of Andean Condors. By chance, ten adult condors had been fitted with GPS tags seven months before the eruption, allowing the researchers to follow their movements with precision. Following the volcanic eruption, ten more condors were given tags.
When the volcano erupted, it ejected 950 million tons of ash into the atmosphere, with an initial column reaching 12 km (7.5 miles) into the sky. Drifting to the east, the ash blanketed 24 million hectares (92,000 square miles). Silica was the major constituent of the ejected ash, which caused blindness, gastric distress and death to livestock, particularly sheep, over the following three months.
Inhabitants of the Andes Mountains, Andean Condors are large, mobile scavengers that feed mainly on carcasses of large and medium-sized mammals. Like sheep. So when the Puyehue volcano erupted, condors in the area faced a choice. Should they stay in the area and take advantage of a sudden rich feeding opportunity, but risk being harmed by the ash, or should they leave behind the habitat that they knew well in an attempt to live out the catastrophe elsewhere?
Alarcón and his coworkers predicted that condors would change their behaviours over time, initially avoiding the potential damage of the volcanic ash, later moving back to take advantage of the opportunity to eat dead livestock, but then avoiding those affected areas after the food had been depleted.
Did that happen? “Interestingly,” wrote Alarcón et al., “no strong eruption-induced effects were apparent on the movement behavior of the condors studied… Overall, our results suggest that the studied birds maintained their general movements patterns after the volcanic eruption and remained largely exposed to the conditions imposed by the catastrophe.”
Perhaps conditions were not sufficiently severe after the eruption to change condor behaviour. Maybe the availability of food is not limiting for condors in this region, so that they didn’t need to take advantage of additional dead livestock. It could be that the advantages of being in an area and social situation that they knew well were greater than the risks of exposure to ash. Abandoning a breeding area comes with the risk that the individual might never get it back.
For the livestock of the region, the eruption of the Puyehue volcano was a catastrophe. For Alarcón and his colleagues, the eruption was serendipitous.
Alarcón, P. A. R., et al. 2016. Movement decisions in natural catastrophes: how a flying scavenger deals with a volcanic eruption. Behavioral Ecology 27:75-82.
Photo credits: Andean Condor stamp from Argentina – www.stampboards.com; Puyehue volcano eruption – www.guardian.co.uk
Week 17 – 30 October 2016:
Where Did You Say It Is?
There cannot be too many bits of land that humans have never visited. There are, however, places that people have found and occupied, but later abandoned and forgotten. In contrast, birds tend to discover sites, settle in, and stay. Some of us dream of travelling to sites that have been abandoned by everything except birds.
Swains Island is just such a locale. A circular atoll in the South Pacific Ocean, the island is part of the Tokelau group, which are a dependency of New Zealand. Swains Island itself is administered by the United States under the umbrella of American Samoa. It is, quite frankly, hard for me to imagine why the United States would want anything to do with Swains. The island is about 2 km long and 1.5 km wide, with a central lagoon full of brackish water. Nowhere does the island poke more than 9 m above the sea, and drinking water is hard to collect. The island’s dominant plant is the coconut palm, but shorefront shrubland, marsh and forest can also be found. Although Swains Island was a coconut plantation in the past, and was occupied year-round, it is now completely uninhabited.
Except, of course, for periodic visits by biologists curious to see which creatures call the island home. The most recent visit was by members of the Department of Marine and Wildlife Resources in American Samoa in September of 2012. Andrew Titmus, conducting research in American Samoa for a doctoral degree at the University of Hawaii, was invited to inventory birds on the island while other researchers looked at insects, coconut crabs, sea life and vegetation. Another key member of the group was Nicole Arcilla, the chief wildlife biologist of DMWR. The group visited Swains Island for six days, 36 years after the previous survey.
Titmus explained to me that the team got to Swains on a chartered boat that normally ferries people American Samoa and Western Samoa. “The journey took the better part of a day and once there we needed to use a small boat to ferry equipment and supplies to the island through a small opening in the reef.”
Titmus and his crew walked the coastline of the island twice, counting every bird they encountered. They documented the birdlife along nine transects through the island’s vegetated habitat, starting at the coast and ending at the central lagoon. They also spent three evenings at sea, watching for rare or transient bird species.
The efforts of Titmus et al. revealed 19 species of birds, some rare and some common. Almost all were seabirds or shorebirds. The Bristle-thighed Curlew, Sanderling, and Brown Booby were represented by just two individual each. In contrast, 7,092 Black Noddys and 4,412 White Terns were counted.
To anyone familiar with waterbirds, it is interesting that: “All nesting and roosting seabirds were observed within trees, with no birds present on the ground or beach.” Titmus and his crew attributed this behaviour to introduced predatory mammals. Even though the island’s feral pig population has been eradicated, there is still a small group of feral cats, and Pacific rats were common everywhere.
This lead Titmus et al. to a wonderful suggestion. If a concentrated effort was to eliminate the cats and rats on Swains Island, and if coconut palms were replaced by native trees that better suited birds, the island could become an important site for nesting seabirds. It is even possible that shearwaters that burrow into the soil to nest might take up residency on Swains.
Titmus wrote to say that “while we were on the island, we camped on the beach by the old village site and copra shed, and there is still the remains of a trail between the village site and the family residence site where there is a dilapidated house and a small graveyard.” To me that sounds like a pretty idyllic spot to study birds.
Titmus, A. J., N. Arcilla and C. A. Lepczyk. 2016. Assessment of the birds of Swains Island, American Samoa. Wilson Journal of Ornithology 128:163-168.
Photocredits: Map of Swains Island - www.janeresture.com/tokelau_islands/swains.htm; Black Noddy with chick by Pete Leary (US Fish and Wildlife Service) - www.usgs.gov/media/images/black-noddy-chick
Week 16 – 23 October 2016:
Irony in the World of Birds
It would probably be quicker to list all of the places where House Sparrows cannot be found. Native to Europe and large swathes of Asia, the Middle East and Africa, it has been successfully introduced to North and South America, the Caribbean, Australia, New Zealand, Hawaii, Mauritius and so on. Adaptable in the extreme, according to a 1993 book by Clement, Harris and Davis, “especially remarkable being the birds that lived and bred 640 m down a coal-mine in South Yorkshire, England, living on food provided by miners.” The closely-related Tree Sparrow also has a wide breeding distribution in Europe, Asia and the Middle East, and has been introduced to Sardinia, the United States, India, Indonesia, Hong Kong, Borneo, Australia, and, well, you get the picture.
Are you ready for some irony? Although there may be as many as 540 million House Sparrows in the world, and perhaps 570 million Tree Sparrows, significant population declines in some regions have caused concern. The British Trust for Ornithology estimates that the U.K. House Sparrow population has declined by half in recent decades, and the city of Edinburgh is said to have lost 90% of those birds between 1982 and 1998. What is going on?
Martin Šálek of the Academy of Sciences of the Czech Republic, and Jan Riegert and Stanislav Grill of the University of South Bohemia investigated House and Tree sparrows in the community of České Budějovice. With 94,000 inhabitants, it is the largest city in the Czech Republic’s South Bohemia region. Better known for its industry than its sparrows, České Budějovice is the home of Koh-i-Noor Hardtmuth pencils and the Budweiser Budvar brewery.
In May of 2013, Šálek and his crew documented every House and Tree sparrow and every nest within the 19.2 km2 (7.4 miles2) spread of the city. On foot and on bicycle, they travelled the city’s streets and parks, peeped over fences, and listened for diagnostic chirping. Dividing the city into 675 plots, each 200 by 200 m (10 acres), they noted the type of habitat found in each plot, including residential sites, parks and cemeteries, and industrial and commercial areas.
Šálek et al. recorded 2251 House Sparrows and 537 Tree Sparrows. House Sparrow densities were highest in residential areas, and were comparatively abundant in the city centre. “High” is a relative term in this case, and House Sparrow densities were much lower than in many other European cities. Tree Sparrows are less dependant on urban landscapes, preferring gardens to residential sites in České Budějovice, they were not seen in the city centre. It seemed “that both sparrows are associated with diverse and mixed habitat composition, where they can find suitable foraging and nesting conditions.” This is particularly true in the breeding season, when adults need to find insects to provide a protein-rich diet for their nestlings.
Even though they are quite flexible, both sparrows built the majority of their nests in crevices and holes in buildings. The older the building, the better. The modernization of old buildings is likely to result in population declines in these sparrows.
“Nesting opportunities could,” explained Šálek et al., “be improved by simple and cheap solutions.” In the reconstruction of old buildings, architects might allow for access for sparrow to nesting sites. New buildings could incorporate cavities for sparrows and other urban birds. Solutions to environmental problems are not always costly or complicated.
Šálek, M., J. Riegert and S. Grill. House Sparrows Passer domesticus and Tree Sparrows Passer montanus: fine-scale distribution, population densities, and habitat selection in a Central European city. Acta Ornithologica 50:221-232.
Photocredits: Eurasian Tree Sparrow stamp - philatelicbirds-art.blogspot.com.au; male House Sparrows - www.theguardian.com
Week 15 – 16 October 2016:
To Feed Or Not To Feed
In some parts of the world, people are able to add substantially to the lives of birds by maintaining birdfeeders. For a modest outlay for lumber, nails and seed we can contribute to the nutrition of granivorous birds in our yards. For a similarly-small sum spent on glassware and sugar, we might attract nectar-feeding birds. The British Trust for Ornithology is involved with bird feeding through its Garden Bird Feeding Survey (www.bto.org/volunteer-surveys/gbfs), as is the Cornell Lab of Ornithology in the U.S. through its Project FeederWatch (feederwatch.org).
Feeding birds is not a one-way gift. Feathered friends reward our generosity by living their lives a little bit closer to ours. Moving from the individual to the wider community, supporting wild birds helps to establish and maintain important links between citizens and nature.
That is not to say that feeding birds is necessarily always positive. Amoung the possible risks are increased disease transmission among birds crowding around feeders, added attention by predators, and the creation of dependency on our generosity. Could it be that feeders also result in increased bird mortality through collisions with the windows of residential buildings?
Justine Kummer, an M.Sc. student at the University of Alberta, and her supervisor Erin Bayne, investigated the possibility that a birdfeeder on a residential property could increase the likelihood of fatal collisions of birds with windows. Their study was conducted in 2014 and 2015 at 43 homes in and around the city of Edmonton in central Alberta, Canada. Some studies of bird biology are more interesting to the public than others, and the study of Kummer and Bayne attracted considerable media attention. The Canadian Broadcasting Corporation was particularly helpful in recruiting homeowners in the Edmonton area to the study. Birdfeeders were erected and stocked with seed, and collisions at windows close to feeders were compared to incidents at windows with no feeders. Homeowners were asked to make daily checks for evidence of collisions by birds.
Over the year-long study, 145 birds collided with windows. Of these, 89 survived and the outcome for another 45 was unknown; only 11 fatalities were reported. Seedeaters like House Sparrows, Blue Jays and Dark-eyed Juncos were among the birds involved in collisions. Curiously, birds not expected to eat grain sometimes struck windows, including Cedar Waxwings and American Robins. This was, presumably, not a consequence of birdfeeders.
The presence of birdfeeders roughly doubled the number of collisions with windows. However the story isn’t as simple as that. Variability in the data was considerable. Far fewer birds struck windows in winter than in any other season, even though non-migrants made greater use of feeders in winter. Of the 43 homes in the study, owners at 18 did not report even a single bird collision, but four homeowners reported a combined 76 strikes, and a single window was responsible for more than 11 collisions. “This suggests that the effects of a bird feeder are dependent on the house and the window,” wrote Kummer and Bayne. “Overall, some houses have a much higher risk than others, suggesting that impacts of feeding birds may be context dependent.”
Having successfully defended her M.Sc. thesis, Kummer is now considering the future. She wrote to say that “I’m very interested in science outreach and education, and science communication – which was a large part of my overall project.” Please join me in wishing her great success in that field.
Kummer, J. A. and E. M. Bayne. 2015. Bird feeders and their effects on bird-window collisions at residential houses. Avian Conservation and Ecology 10(2):6.
Photo credits: Blue Jay at a feeder – www.uniquebirdhouseboutique.com; Cedar Waxwing – www.allaboutbirds.org
Week 14 – 09 October 2016:
When a Tree is Not Just a Tree
Birds have an uncanny ability to fill our lives with joy by simply being there. In the depths of a Australian summer, under the cruel, baking sun of the outback, it takes just a small waterhole to attract Zebra Finches. On a dimly-lit morning in the coldest part of a Canadian prairie winter, a bird feeder stocked with seeds will attract House Sparrows. Wherever you are in the world, birds are there to be seen.
But we need to take care. The mere presence of birds does not guarantee that all is well with the world. In our near-limitless capacity to transform the landscape, we may be making subtle changes. It sometimes takes a keen eye to notice that change.
Fabrico Cid and Enrique Caviedes-Vidal of the Universidad Nacional de San Luis in Argentina recently published a paper concerning human-created changes to the birdlife of a region around a reservoir. The Embalse La Florida was constructed between 1945 and 1953, and serves as the main source of drinking water to the cities of San Luis (170,000 residents) and Villa Mercedes (111,000 residents). The reservoir has an area of more than 650 ha (1,600 acres) and a circumference of 36 km (22 miles), and provides recreational opportunities in the form of swimming, fishing, kayaking and windsurfing. That all sounds pretty good, right?
A portion of the land around the reservoir is a combination of native woodlands, Acacia shrubs and grasslands, but the remainder has been modified as small-scale tree plantations in support of campsites and a settlement. The plantations are dominated by trees not native to Argentina such as pine and eucalyptus.
Cid and Caviedes-Vidal surveyed the bird populations of the natural habitat and tree plantations in both the breeding and non-breeding seasons. They documented almost 3000 birds of 75 species. The smallest was the 5 g (0.2 ounce) Yellow-billed Tit-tyrant, and the largest was the 1.9 kg (4.2 pounds) Black Vulture. Spot-winged Pigeons were far more abundant than any other species.
In both the breeding and non-breeding seasons, bird abundance was higher in tree plantations than among native plants; species richness was similar between the two habitat types. Even though the distances between sites was short, most bird species were seen in one habitat type or the other, but not both. Cattle Tyrants, Monk Parakeets and Brown Cacholotes were only seen in the plantations, whereas Pale-breasted Spinetails and Southern Bearded-tyrannulets were seen only in the natural habitats. Plantations favored large-bodied generalist feeders; native vegetation favored smaller-bodied birds that feed within the foliage of the plants.
Changing the landscape changes the composition of the bird population within it. Although no birds of special conservation concern were recorded by Cid and Caviedes, the authors pointed out that the area covered by tree plantations could grow substantially in the near future. Loss of natural habitat is likely to have consequences for birds that rely on those conditions. With an expanding human population, it may become necessary to set aside patches of native vegetation in the region. Biological diversity is a matter of variation as well as abundance.
Cid, F. D. and E. Caviedes-Vidal. 2014. Differences in bird assemblages between native natural habitats and small-scale tree plantations in the semiarid midwest of Argentina. Wilson J. Ornithol. 126:673-685.
Photo credits: Yellow-billed Tit-tyrant © Jorge Martín Spinuzza (www.avespampa.com.ar & neotropical.birds.cornell.edu); Brown Cacholote © Karl-Fredrik Sjolund - buenosairesbirding.com/birds
Week 13 – 02 October 2016:
I Love Birds, But…
A child who wanted to create a picture of a Blue Swallow would only need one crayon – Midnight Blue. These birds are deep metallic colour all over, and sport a pair of very long tail feathers. Blue Swallows breed in southern Africa and spend the non-breeding season further north in Kenya and Uganda. Regrettably, very few children are likely to know what a Blue Swallow looks like. Just 3000 members of this species remain, and those are thinly distributed. There are more people living in Thermopolis, Wyoming, than there are Blue Swallows in all the world. I have been to Thermopolis. It isn’t big. Southern Africa is.
According to preliminary observations, it seemed that a substantial breeding population of Blue Swallows might reside in the southern Tanzanian highlands. Steven Evans and colleagues at the University of Venda, North-west University (both in South Africa), and the Tanzanian Bird Atlas Project recognized the pressing need to quantify the swallow’s abundance in the region. Ideally they would also be able to determine the bird’s habitat preferences, and current threats to that habitat.
Evans and his team conducted two surveys of Tanzania’s Kipengere Mountain Range; once in 2008/2009, and again in 2012. The team surveyed 3,635 km (2260 miles) of grasslands, pastures, croplands, villages, and tree and tea plantations. (For perspective, this is greater than the distance from Thermopolis, Wyoming, to Montreal, Quebec, or between Strasbourg in France and St. Petersburg in Russia.) For each swallow sighting, GPS coordinates, altitude and habitat type were recorded. The group found nests of Blue Swallows by searching the undersides of bridges and by asking locals.
The total of 151 Blue Swallows and 14 nests were recorded at 62 localities. Considering the total area searched, and by estimating the total area suitable for the species in that part of Tanzania, Evans and crew felt that the region was likely to support between 602 and 1362 individuals. Clearly, the southern Tanzanian highland grasslands support a significant proportion of the world’s population of Blue Swallows, particularly in natural pastures and around villages. “This finding indicates that the development of rural villages is not a threat to the birds,” wrote Evans et al. Indeed, Blue Swallows may be feeding on insects attracted to livestock and dung, and buildings in villages may provide a suitable surface for the construction of swallow nests. It is even possible that artificial structures could be erected to facilitate swallow nesting.
Evans and his coworkers described the need for similar swallow surveys in the Marungu Highlands and Upemba National Park in the DRC. If they are currently planning such work, then they must be braver than I. On its website: “Global Affairs Canada advises against non-essential travel to the Democratic Republic of Congo… points of entry from Burundi, Rwanda and Uganda should be avoided at all times because of continuing insecurity and lawlessness in those areas… Crime is endemic in the DRC as a result of extreme poverty and the prevailing climate of impunity.”
I love birds, but not enough to get killed while conducting a survey.
Evans, S. W., E. M. Baker, N. E. Baker and D. Cillers. 2016. Current distribution and population size of the Blue Swallow Hirundo atrocaerulea in the southern Tanzanian highlands. Ostrich 87:37-46.
Photo credits: male Blue Swallow, The Handbook of the Birds of the World Alive - http://www.hbw.com/species/montane-blue-swallow-hirundo-atrocaerulea; female Blue Swallow photograph by Warwick Tarboton (copyright Warwick Tarboton) – www.warwicktarboton.co.za/index.html
Week 12 – 25 September 2016:
That Seems Like a Lot of Foolin’ Around
As I described in an earlier entry, birds are a model of monogamy. There are lots of exceptions, but a bird family usually consists of a mom, a dad and a nest full of happy chicks. This system of mating is attributed to the value of having two parents attending to the needs of their dependent nestlings.
With the advent of genetic technologies, it became possible to determine with certainty whether the social father of nestlings was also their genetic father. It came as a surprise to many researchers to find that, for a wide range of bird species, chicks were frequently the product of a male other than their social father.
The benefit to males of extra-pair copulations is obvious. By sneaking on to the next territory to copulate with a female to which he is not mated gives him the opportunity to pass along more of his genes without the additional cost of caring for the young. The possible risk to the male is that while he is being sneaky with the neighbouring female, another male might be doing the same thing with his mate.
Benefits of extra-pair copulations to females are a little more subtle. By engaging in such behaviour, a female might be protecting herself against the possible infertility of her social mate. She may also be able to copulate with a male that is genetically superior to her mate, resulting in better offspring.
Members of some bird groups seem to do a great deal of foolin’ around. Studies of raptors, on the other hand, have shown that very few chicks are not genetically-related to their social fathers. In part this may be because mated birds of this sort copulate with impressive frequency. Or at least that was the story until now…
In a recent publication, Robert Rosenfield and his colleagues at the University of Wisconsin and the Alaska Science Center showed that Cooper’s Hawks, Accipiter cooperii, are an exception. Studying a breeding population of hawks in Milwaukee, USA, the team collected blood samples from as many adults and chicks as they could. They used a decoy Great Horned Owl to cause adult hawks to fly into a net so that blood samples could be taken; Rosenfield told me that the decoy’s name was LE, pronounced “Lee.” It was a small male, and so looked a bit like a Long-eared Owl.
The team found genetic evidence of a remarkably high incidence of infidelity. Nineteen percent of Cooper’s Hawk chicks in this region were not the product of their social father, and 34% of all broods contained at least one illegitimate chick. Could this be because mated Cooper’s Hawks copulate less frequently than other raptors, allowing greater opportunity for fertilization by other males? Apparently not. In an earlier publication, Rosenfield reported that in the thirty days before egg laying, pairs of Cooper’s Hawks averaged more than twelve copulations a day.
What is the cause of all this foolin’ around in this socially monogamous bird? It seems that male Cooper’s Hawks provide food to their mates, and that food delivery is often followed by copulation. Could it be that females are accepting copulations from additional males, and possibly even soliciting them, in exchange for food before the energetically-demanding period of egg production? The breeding population of Cooper’s Hawks in Milwaukee is particularly dense, and the urban environment is rich in food. Their diet includes sparrows, robins, starlings, doves and chipmunks. Rosenfield et al. suggested that this may make it easy for “females to encounter extra-pair males with prey and trade copulations for food.”
Rosenfield, R. N., S. A. Sonsthagen, W. E. Stout and S. L. Talbot. 2015. High frequency of extra-pair copulations in an urban population of Cooper’s Hawks. Journal of Field Ornithology 86:144-152.
Photo credits: Cooper’s Hawk photograph by Johann Schumacher - www.audubon.org/field-guide/bird/coopers-hawk; Cooper’s Hawk stamp – www.birdtheme.org
Week 11 – 18 September 2016:
“Over Here! Look at Me! Over Here!”
Some birds are much better-known than others. Let me offer you the following evidence. If a biologist is keen to find scholarly publications addressing a particular topic or species, she might use an academic search engine called Web of Science. Using “Turdus merula,” the scientific name of the Eurasian Robin, as a search term will return 680 recent papers, and “Zonotrichia leucophrys,” the White-crowned Sparrow, will reveal 730 publications. Neither of those come close to “Anas platyrhynchos,” the Mallard duck, which will lead to 2,649 papers.
Pity, then, the poor Pygmy Wren-babbler. When I entered its scientific name, “Pnoepyga pusilla,” into Web of Science, I was offered just two publications. One was a 2013 paper which considered the relatedness of all members of the genus. The other was a 1991 publication about an entirely different type of bird.
It isn’t that the Pygmy Wren-babbler isn’t interesting. It is. At just 8 cm (3 inches) in length, and with no tail to speak of, this wren-babbler looks very much like an olive-brown egg adorned only by a tiny black beak and oversized legs. Seven subspecies are recognized, and some of these should probably considered as full species. Four distinctive forms are found on the islands of Indonesia alone. Despite being reasonably common in Nepal and China, the little bird just hasn’t been very well studied.
In 2016, Muhammad Nazri Janra of Andalas University in Indonesia and Richard Noske of Charles Darwin University in Australia published a brief note in the journal of the Indonesian Ornithologists’ Union. In November of 2009 Janra and his field crew were using mist-nets to capture birds 1,200 metres up the side of Mount Singgalang in the province of West Sumatra. The study targeted the Sumatran Cochoa, a beautiful and vulnerable songbird known only from Sumatra. While working along a woodland trail, Janra inadvertently flushed a Sumatran Pygmy Wren-babbler (Pnoepyga pusilla lepida) off its nest. The bird hopped along the ground, dragging one wing as though it was broken; it was an act of attempted deception. Janra was able to find the nest, even though it was very well concealed. Situated 50 cm (20 inches) above the ground, and constructed of plant fibres and covered with moss, it contained two white eggs.
The broken-wing display has been described most frequently from ground-dwelling shorebirds such as killdeer and other plovers. This strategy is surely designed to draw predators away from nests, although it requires great attention by the adult if it is to avoid being pounced upon. Not only was this the first observation of the broken-wing display by any member of the genus Pnoepyga, but it represents only the second published record of breeding by the species on Sumatra. It is a reasonably common bird on the world’s sixth-largest island, and yet we know almost nothing about it.
Their work required Janra and his team to investigate other locales. When they revisited the site where the broken-wing display had been witnessed a month earlier, they were unable to locate the nest nor spot any Pygmy Wren-babblers, and so it is not clear whether the nesting attempt had been successful.
It is through the dedication of researchers like Janra that we come to a better understanding of the world of birds. One observation at a time.
Janra, M. N. and R. Noske. 2015. Sumatran Pygmy Wren-babbler Pnoepyga pusilla lepida performing broken-wing distraction display near nest. Kukila 18:62-64.
Photocredits: Pygmy Wren-babbler – drawing of a Sumatran Pygmy Wren-babbler - http://www.hbw.com/species/pygmy-wren-babbler-pnoepyga-pusilla; http://www.birdingintaiwan.com/pygmywren-babbler.htm
Week 10 – 11 September 2016:
Waste Not, Want Not
The efforts of dedicated biologists enlarge our understanding of bird biology with their discoveries. After years of work in the field and laboratory, results are published in the pages of scholarly journals so that they can illuminate others, now and into the future. That is one of the interesting things about scientific journals – with any luck, their contents will continue to be available to researchers for centuries to come.
I recently pulled a ninety-year old copy of the journal The Condor: A Magazine of Western Ornithology off a shelf in my personal library. The copy was Issue 1 of Volume 28. Along with journals like Ibis and The Auk, it represented a repository of the best new findings of bird enthusiasts, with particular emphasis on the west coast of North America.
By today’s standards, much of the content of the 56-page copy in my hand would be considered natural history, rather than science. The first thirty pages were a consideration of bird husbandry in British aviaries, written by Casey Wood of Kandy, Ceylon (now Sri Lanka). This was followed by short pieces on the appearance of Franklin Gulls in Colorado, the consumption of frozen insects by American Dippers, and the vocal behaviour of Band-tailed Pigeons. One article was particularly revealing, not just of the birds being studied, but also of the writer.
Ernest D. Clabaugh explained that he had been engaged in banding (“ringing” in the UK) nestling Western Screech-owls. He noted the remains of meals brought by the parents to their chicks. Most of these were House Sparrows, supplemented by gophers, mice and salamanders. “It is interesting to note,” wrote Clabaugh, “that practically all of the birds found in the nest had their heads eaten off when I found them.”
Even more interesting to me is Clabaugh’s honesty. At 05:30 on 3 June, 1924, he dropped one of the young owls while banding it. The bird appeared to be injured, but he applied band number 223576, and put it back in the nest. When Clabaugh returned to the nest the next day: “the leg of no. 223576, which held the band, was all that was left of this bird. It was in the nest, the bird apparently having been eaten by the three remaining young owls.”
I found a few details of the life of Clabaugh. A resident of Berkeley, he trained as a civil engineer at the University of California, but his great joy appeared to be the lives of birds. Over a period of 30 years, Clabaugh banded many thousands of birds, an activity he continued to his death in 1953. He served on the executive of the Western Bird Banding Association, and the Cooper Ornithological Club, the group that published The Condor. He was also a very honest man.
Clabaugh, E. D. 1926. Notes of the food of the California Screech Owl. Condor 28:43-44.
Photo credits: Western Screech Owl, Oregon Zoo – www.oregonzoo.org; Western Screech Owl stamp – www.pinterest.com
Week 9 – 04 September 2016:
According to its website, Adolfo Suárez Madrid-Barajas Airport in Spain is: “One of the airport capitals of the 21st century.” How exciting! Its four runways have a combined length of 15.5 km (9.6 miles). Four terminals provide for 71 airlines serving 182 domestic and international destinations. Forty-six million passengers used the airport in 2015, which is more than 126,000 travellers each day. All those busy people, and a few birds.
In recent years, the impact on wildlife of noise created by human activities such as traffic and construction has become a topic of considerable interest. Birds in particular seem to be vulnerable to disturbance by human-created noise, if only because many birds use acoustic cues to help avoid predation. What better situation to study the impact of noise on birds than the nosiest spot of all – a busy airport?
In a recent publication, Ignacio Klett-Mingo and Diego Gil of the Universidad Politécnica de Madrid, and Ignaco Pavón of the Museo Nacional de Ciencias Naturales described the results of their study of aircraft noise at Madrid-Barajas airport on the local birdlife. The airport is bordered by a river and a woodland, home to a substantial bird community. When arriving and departing airplanes pass the woodland, peak noise levels can exceed 85 dB. This level of noise is apparently sufficient to cause permanent hearing damage in humans after just eight hours of exposure.
Klett-Mingo and his colleagues placed six bird feeders in the study area, stocking them with peanuts. They documented the behaviour of Great Tits using video recorders placed close to the feeders. Birds living next to a busy airport runway are unlikely to be surprised when an airplane arrives or departs, but do these events disrupt their lives?
Klett-Mingo et al. found that tits changed their behaviour significantly as airplanes passed by. Birds spent less time feeding and more time with their heads up, scanning their environment, spending almost twice as much time being vigilant when aircraft noise was greatest. It seemed as though tits found it necessary to be more vigilant when their world got noisy.
This isn’t surprising. Great Tits, like many other birds, rely on acoustical signals to help warn them about potential predators. For instance, some birds produce alarm calls in threating situations, allowing other birds around them to respond in an appropriate way. When lots of individuals are watching for danger, these signals can allow each of them to spend less time being vigilant, and more time foraging. When things get too noisy, the value of these social signals are lost, and each individual needs to be more wary.
The lost foraging time might be particularly harmful in winter when days are shorter and food is less available. Beyond food challenges, Klett-Mingo speculated that repeated loud noises might increase physiological stress in birds living near runways. Perhaps the increased vigilance by individual tits cannot fully compensate for aircraft noise, resulting in an increased risk of predation, particularly if the noise leads to distraction.
Diego Gil explained to me that there are many bird predators in the study area, including Eurasian Sparrowhawks. The main cause of this abundance is likely the absence of hunting pressure around the airport, but it is also possible that airplane noise makes potential victims more vulnerable, and so the habitat is more valuable for foraging by predators.
Birds do not wear noise-cancelling headphones. Wouldn’t it be interesting to know whether Great Tits exposed to the roar of aircraft at Madrid-Barajas Airport suffer hearing loss?
Klett-Mingo, J. I., I. Pavón and D. Gil. 2016. Great Tits, Parus major, increase vigilance time and reduce feeding efforts during peaks of aircraft noise. Animal Behaviour 115:29-34.
Photo credits: Great tits playing with a camera, photographed by Vadim Trunov – www.express.co.uk/news/nature/624939/amazing-picture-squirrel-and-bird-messing-around-with-camera; first day cover of Great tit and Hortensia stamps from Spain, sent to collector Florian Tirk – worldwidecovers.wordpress.com/2009/09/
Week 8 – 28 August 2016:
Well, That’s Okay If You Are A Seal, But…
Several years ago New Scientist magazine described Bouvet Island in the far south Atlantic Ocean as the only place on Earth not to have had any plant or animal species introduced by humans. It is also the locale for the 2004 horror/sci-fi film Alien vs. Predator. Further, it is one of the few places I can think of without a single bird that isn’t a seabird. Bouvet Island is almost entirely covered by ice and is, quite possibly, the most remote bit of land on the planet.
That did not deter Corne Niemandt of the University of Pretoria and seven of his colleagues from Norway and South Africa. They recently published a report on their findings concerning penguins that breed on Bouvet Island, also known as Bouvetøya. The team visited the largest ice-free spot on the island during four penguin breeding seasons between 1997 and 2008. They were particularly interested in the food brought to Chinstrap Penguin and Macaroni Penguin chicks. If we hope to understand the possible impacts of global climate change on wildlife species, then we must first understand fundamental features of their biology such as what they eat.
Adult penguins and their chicks were counted, and samples were collected from the stomachs of adult penguins during the chick-rearing period. Niemandt et al. found that Chinstrap Penguins were extremely picky eaters. Of 56 samples, all contained a type of krill with the scientific name Euphausia superba, and this one creature constituted more than 99% of the mass of stomach contents. The study population consisted of between 350 and 500 Chinstrap Penguins from 1996 to 2001. When counted again in 2008, the combined population of adults and chicks had declined by more than 80%.
Macaroni Penguins at Bouvet were more flexible in their diet. Krill were still a common food, but a range of fish species such as Electrona carlsbergi and Krefftichthys anderssoni were also eaten. The population of Macaroni Penguins declined, but not as severely as did Chinstraps.
What caused the decline in Penguin populations? Perhaps food was became less abundant, either because of physical changes in the environment or increased competition with other species such as krill-feeding whales. Niemandt and his colleagues found that most penguins were able to maintain two chicks each year, “suggesting that breeding birds are finding enough food.” Instead, it seems likely that declines in breeding penguin numbers resulted from a lack of breeding space. The breeding population of Antarctic fur seals has increased in recent years, and their colony now occupies almost all of the available space, displacing the penguins. Bouvet Island has the world’s second largest Antarctic fur seal population, with something like 66,000 of them occupying the beach where penguins attempt to breed. Landslides close to cliff edges have probably also contributed to penguin declines, displacing some and killing others.
But wait a minute… The study included a spell in the 2007/2008 Austral summer, right? According to online sources, the field station at Bouvetøya had been destroyed in 2007, likely as a result of an earthquake followed by a severe winter storm. I contacted Kit Kovacs of the Norwegian Polar Institute in Tromsø, and corresponding author on the penguin paper. She explained to me that the crew operated under difference circumstances in 2008. “The tent was a super insulated Canadian product that made a fine home for the crew,” she wrote. “We have a wonderful new station now, so the tent is old news and fading from memory.” One member was bitten by a fur seal that year, but those are the sorts of risks that a field biologist has to deal with. The scar probably serves as a reminder of a productive summer spent in a very, very remote spot.
Niemandt, C., et al. 2016. Chinstrap and Macaroni penguin diet and demography at Nyrøysa, Bouvetøya. Antarctic Science 28:91-100.
Photo credits: Chinstrap Penguins, photo by Pete Morris – www.birdquest-tours.com; Macaroni Penguins - knowledgebase.lookseek.com
Week 7 – 20 August 2016:
When Snakes Control the Show
Why might a female Acadian Flycatcher in Connecticut choose to produce three eggs instead of four? Why would a Eurasian Blackbird overwintering in northern Africa choose to fly all the way to Iceland to breed instead of staying put? Why would a Shiny Cowbird in Argentina choose to lay its eggs in the nest of a Rufous-collared Sparrow instead of raising its own chicks? The world of birds is full of odd life history riddles that all seem to have the same solution. By behaving one way instead of another, an individual is attempting to maximize its lifetime reproductive success. As with anatomical and physiological characteristics, many behaviours are shaped by natural selection.
So why, then, do Japanese Scops-owls and Ryukyu Scops-owls, birds of roughly the same size and shape, living in the same place at the same time, choose to breed more than a month apart?
The question was recently tackled by Masahiro Toyama and colleagues from Hokkaido University and the Kyushu Research Centre. Their study sites were the Kunigami Forest Park and Yona Experimental Forest on Okinawa Island, Japan. One of an island chain, and part of Japan’s southern-most prefecture, Okinawa and its forests are subtropical, without the very large seasonal differences in climate found in temperate regions.
Their subjects were two species of scops-owl, a group of about 70 species, known for their small size and spectacularly complex classification. Both the Japanese and Ryukyu scops-owls are comparatively small, between 20 and 25 cm (8 to 10 inches) tall, and I would probably have trouble telling them apart even if I had one in each hand and a field guide open between them.
Even so, these birds are, most certainly different, and the timing of their breeding seasons was sufficiently dissimilar to attract attention. Toyama et al. utilized cameras and nest boxes to look into the factors that might have shaped this difference in timing.
They found that mean egg-laying date of the Japanese Scops-owl was 17 March, with young departing their nests between early May and early June. The mean egg-laying date of Ryukyu Scops-owls was 8 May, and young did not leave the nest until late June to mid-July. Curiously, while Ryukyu Scops-owls averaged 2.76 eggs per nest, and the Japanese Scops-owls averaged just 2.29 eggs per nest, there was no difference between the species in the mean number of young that survived to leave the nest.
How did Toyama and his colleagues resolve the puzzle? The Ryukyu Scops-owl is a dietary specialist, feeding mostly on bush-crickets. These birds can only breed later in the Spring when their insect food is abundant. Unfortunately, this is the time of year when it is warm enough for the principal predator of eggs and chicks, the Ryukyu odd-tooth snake, to be active. The Japanese Scops-owl is able to avoid most of the predation of its eggs and chicks by snakes by breeding earlier in the cooler part of Spring. Being a dietary generalist, feeding on insects, centipedes, and small reptiles, birds and mammals, a Japanese Scops-owl can feed its chicks when a Ryukyu Scops-owl couldn’t. Individuals of both species are doing what they can to raise as many chicks as possible.
When I contacted him, Toyama explained that he has been investigating species differences in nest site selection by different scops owls. It seems that the decision to build a nest in one spot instead of another is related to seasonal changes in predation risk. Competition between members of the two owl species may also help to drive their differences in breeding season. I asked whether the Ryukyu odd-tooth snake was a problem for researchers on Okinawa. Toyama reassured me that these snakes are non-venomous.
Toyama, M., N. Kotaka and I. Koizumi. 2015. Breeding times and nest predation rates of sympatric scops owls with different dietary niche breadth. Can. J. Zool. 93:841-847.
Photo credits: Scops Owl stamp, designed by Israeli artist Miriam Karol (1926-1994), Israel, 1963 - au.pinterest.com; photograph of a Ryukyu Scops owl – shortwing.co.uk
Week 6 – 14 August 2016:
Europe’s Most Endangered Songbird?
Without taxonomy, there is no biological conservation. It really is that simple. We don’t enact laws to protect creatures, or gather funds for projects to help restore their numbers, until we know exactly what we are dealing with.
And therein lies the problem. Birds are the best-studied wildlife group on the planet, yet we still don’t fully understand who is related to whom; the classification of birds is in a constant state of flux. It is one of the key goals of avian biology to understand how one group of birds is related to another, and each new finding is likely to result in a change in the system of classification.
Consider the Blue Chaffinch. According to the Avibase website (http://avibase.bsc-eoc.org), this resident of two of the Canary Islands off the northwest coast of Africa is also known by the common name Teydefinch. Its two-part scientific name is Fringilla teydea, first applied to the species in 1841 by biologists Webb, Berthelot and Moquin-Tandon. Fringilla is Latin for “finch,” and teydea is a reference to Mount Teyde on the island of Tenerife.
So far so good?
In 1905, the German ornithologist Ernst Hartest subdivided the Blue Chaffinch into two subspecies on the basis of differences in size and plumage. To the birds on the island of Tenerife, he added a third component to the name, making it Fringillla teydea teydea. Members of the second subspecies, found on the island of Gran Canaria, were to be known by the three-part name Fringilla teydea polatzeki. One species – two subspecies.
Still with me?
According to the IUCN’s Red List of Threatened Species website (http://iucnredlist.org), the Blue Chaffinch should be considered “near-threatened.” The IUCN points out that the subspecies living on Gran Canaria is doing very poorly, but when combined with birds on Tenerife, the species is secure and possibly increasing in size. Laws that protect species do not necessarily apply to threatened subspecies. Consequently, the Gran Canaria form of the Blue Chaffinch might soon be lost.
Enter Swedish researcher George Sangster and four of his colleagues from the Canary Islands, the Netherlands, Portugal and the United States. For the first time since 1905, Sangster et al. reconsidered the taxonomy of Blue Chaffinches. Recognizing the value of utilizing multiple lines of evidence, they first considered differences in the plumage of the two chaffinch groups, studying stuffed specimens in museum collections. The group then recorded the calls and songs of Blue Chaffinches in the wild, and accessed archived recordings, to assess differences between the groups. They also conducted playback experiments in which songs of both subspecies were broadcast to Blue Chaffinches on Gran Canaria to determine whether they could discriminate between songs from their own island and those from Tenerife.
When combined with earlier studies of genetic differences between the groups, Sangster and his colleagues felt that differences in plumage, songs, calls, and responses to playback all pointed to the conclusion that Blue Chaffinches on Gran Canaria and Tenerife are not just subspecies, but rather are different species. Already different, they are likely to continue to diverge in the future. Given that the Gran Canaria form has a very small range (less than 20 km2; 8 square miles) and population (something like 120 individuals), and that the population has been in a long-term decline, Sangster et al. felt that Fringilla polatzeki (a full species) should be considered critically endangered and in need of immediate assistance.
When I contacted him, Sangster responded with great enthusiasm. He even supplied the photograph that accompanies this piece. He explained that he and his colleagues had known for more than a decade that the Gran Canaria population of the Blue Chaffinch was something unique and special, but waited to publish their findings until all of the necessary evidence had been collected, and that local ornithologists were in agreement with the change in status. They were also concerned that an influx of birdwatchers might damage the last bit of habitat available to the birds.
Felipe Rodríguez-Godoy added to the story, explaining that a captive breeding program for the Gran Canaria Blue Chaffinch has been in place for several years. To date 80 juvenile birds, products of the breeding program have been released. The population has been growing very slowly, and so a translocation program has been added. Some of these birds were fitted with radio transmitters so that their progress might be monitored. It will be a couple of years before the effectiveness of the translocation is known.
It is through efforts like these that the future of Europe’s most endangered songbird now looks a bit brighter.
Sangster, G., F. Rodríguez-Godoy, C. S. Roselaar, M. S. Robb and J. A. Luksenburg. 2016. Integrative taxonomy reveals Europe’s rarest songbird species the Gran Canaria Blue Chaffinch Fringuilla polatzeki. J. Avian Biol. 47:159-166.
Photocredits: photograph of a male Blue Chaffinch by Steve Kitchen, from http://birdingaxarquia2.blogspot.com.au/2016/03/the-blue-chaffinch.html; painting of Blue Chaffinches from http://www.avibirds.com/html/Blue_Chaffinch.html
Week 5 – 07 August 2016:
Perhaps We Should Begin Again
It is easy to be captivated by the extraordinary efforts of some birds in constructing their nests. Several days are required for a pair of Cliff Swallows to gather the 1000 mud pellets necessary to build their gourd-shaped nest under a bridge. A male Australian Brush-turkey will continue to maintain and modify his mound of rotting vegetation week after week, for as long as there are eggs to be incubated within it. And if nests can be so very costly to construct, why are members of some species willing to abandon a nest before ever using it?
Christa Benkmann of Deakin University in Australia and Kathy Martin of the University of British Columbia in Canada addressed the question of nest abandonment in Grey Fantails, tiny, insect-eating songbirds native to Australia and New Guinea. Their nests are composed of dry grass and bark, enclosed within a layer of spider webs, with an open top and a stem hanging from the bottom. Fully 71% of nests appear to be abandoned before being used, and a few birds might build as many as seven nests in a breeding season. What is the point of constructing a nest just to abandon it?
Benkmann and Martin examined four possible explanations by monitoring the construction of 194 Grey Fantail nests in the 2012/2013 breeding season.
1. Could it be that what we have interpreted as abandonment was actually “cryptic predation?” Perhaps predators are sneaking in and consuming the eggs before the nest was noticed by researchers. This doesn’t seem to be the case in Grey Fantails, as most nests are abandoned before being completed.
2. Perhaps nests are abandoned after being damaged by extreme weather. Possible, but not likely, as Beckmann and Martin found that only 9% of abandonments occurred within 24 hours of bad weather.
3. Could it be that Grey Fantails are constructing decoy nests in order to dissuade potential predators? If a predator investigated one nest after another but didn’t find anything to eat, perhaps it would abandon its search for nests of that sort. This doesn’t seem likely in the case of fantails as some individuals were seen to dismantle abandoned nests, and reuse old nesting material in the construction of new nests.
4. Only one explanation was consistent with the observations of Beckmann and Martin. It seems that Grey Fantail nests that were under construction, but proved to be poorly concealed from predators, were abandoned. New nests were then constructed in more secure circumstances. Bird predators, particularly Pied and Grey currawongs were observed preying on both eggs and nestlings. As visual predators, superior nest concealment is probably essential to avoiding them.
But what actually cues the fantails, telling them that their current nest might not be in the right place? When contacted, Beckman responded that for daytime predators like currawongs, seeing them near the nest is probably enough to cause fantails to abandon the attempt. “I think mammalian predators might also find the nests after dark – maybe they leave scent cues the birds can use?” Beckman is planning to continue her work in this area, using cameras to identify predators at the nest. Very little is known about nest predators in Australia.
Beckman, C. and K. Martin. 2016. Testing hypotheses about the function of repeated nest abandonment as a life history in a passerine bird. Ibis 158:335-342.
Photo credits: incubating grey fantail - strathbogierangesnatureview.wordpress.com; stamp – www.birdtheme.org
Week 4 – 31 July 2016:
Yawning is an incredible behaviour. We all do it, but no one can say definitively why we do it. Yawning generally happens more frequently when we are tired or bored, but that doesn’t say much about its function. Some researchers have suggested that yawning is a way of cooling the brain, or that it arouses the brain’s cerebral cortex. Whatever the function, it must be pretty important because lots of animals do it, from jewel fish to walruses.
Are you yawning yet? If so, then you are engaged in contagious yawning, the result of seeing others yawn, or even thinking about yawning. Contagious yawning is a far less common behaviour, and had been demonstrated convincingly for just a handful of mammal species.
Recently Andre Gallup and colleagues in the Psychology Department at the State University of New York in Oneonta investigated contagious yawning in a group of captive budgerigars. Given that budgies form long-term pair bonds, and live in coordinated flocks year-round, they seemed like a good test subject. So… can budgies cause each other to yawn?
Gallup et al. observed paired birds in adjacent cages. In some cases, members of the pair could see each other, and in other cases they were visually isolated by an opaque barrier. After 32 hours of observation, and 131 recorded yawns, it was found that a budgie was more likely to yawn if it had seen its companion do the same. It didn’t seem to matter whether the subject was familiar with the bird in the next cage, or if it was a stranger. Budgies were then shown video footage of 150 yawns. This resulted in a modest by significant increased the frequency of yawning.
A link has been suggested between contagious yawning and the ability to empathize with plight of others. If you are a contagious yawner, it may be that you are a more empathetic person. Gallup et al. suggested that budgerigars might serve as a good model for the study of empathy.
When contacted, Andrew explained that his group was continuing their studies of budgie social behaviour, and was interested in a neurochemical basis for their their contagious yawning.
I asked whether bird yawning caused yawns among members of the Bird Yawning Lab. He said: “I did find myself yawning quite frequently when I first began to study yawning, but over the years I have become habituated to yawning stimuli (at least when it comes to research).”
Gallup, A. C. et al. 2015. Experimental evidence of contagious yawning in budgerigars (Melopsittacus undulatus). Anim. Cogn. 18:1051-1058.
Photo credits: budgies – Talkbudgies.com; Australian Post budgerigar stamp – stampboards.com
Week 3 – 24 July 2016:
Eagles and Snakes
There are many reasons why birds are so appealing. Birds are reasonably large, and active during the day, making them easy to spot. Most have exquisite plumage, exhibit interesting behaviours, and are capable of flight which captures the imagination. We share our immediate world with many types of birds. As a consequence, birds are better-known that any other group of plants or animals, and lessons learned about birds are likely to apply to other species. And so our studies of avian biology continue.
In a recent paper, Ezra Hadad of the Israel Nature and Parks Authority, and Gilad Weil and Motti Charter of the University of Haifa pointed out that birds, particularly large species like hawks and eagles, have a special role to play in conservation biology. If we protect birds with large home ranges, they explained, then we protect all of the other plants and animals within that space. However, a thorough understanding of the natural history of a species, particularly the factors that limit its abundance, is necessary for the formulation of effective plans for preservation.
Over three breeding seasons, Hadad and his colleagues studied Short-toed Snake-eagles over a 1,175 km2 (453 mi2) section of the Judea region of Israel. (For perspective, this is nearly one-twentieth of Israel’s entire area). The study area was surveyed at least once a week through each breeding season (March to August). Eagle nesting sites were located by watching for courtship and territorial behaviours, and for adults flying while carrying prey.
As many as 109 breeding pairs of Short-toed Snake-eagles were monitored each year, and the reproductive success of these pairs was as high as 98% – an exceptional result. On average nests were situated about 1 km (0.6 mi) from their nearest neighbours, although two exceptional nests were discovered just 58 metres (190 feet) apart. Perhaps most importantly, regions of natural habitat had a significantly higher density of eagle nests than agricultural areas or human settlements. This may be related to availability of the eagle’s preferred food; as its name implies, this species is particularly fond of snakes. The loss of trees in which the eagles nest is also a concern.
When contacted, Motti Charter explained that Israeli laws against hunting are effective in protecting Short-toed Snake-eagles, but “since the country is small with many borders, birds of prey frequently fly over the borders to hunt and are at risk.” Charter provided me with other fascinating aspects of the natural history of this peculiar species. He said that some of the snakes in Israel are venomous, but that the eagles seem to be immune to the venom. Even so, the snake wins the battle on some occasions, particularly if the eagle attempts to capture a constrictor by the head or the tail, rather than in the middle of the body. As the name suggests, the eagle has short toes, which aids in capturing snakes.
Charter also sent me a link to a camera providing live coverage of a pair of Short-toed Snake-eagles at their nest, which you may wish to see. http://www.birds.org.il/he/tracking-methods.aspx?camId=22.
With a population of 8.4 million, Israel has about as many residents as the American state of Virginia, living on just one-fifth of Virginia’s land mass. According to the Israel Central Bureau of Statistics, the nation’s population is likely to grow to between 10.0 million and 12.8 million by the year 2035. Throughout Israel and other parts of the Middle East, Hadad and his colleagues explained, natural habitat is being encroached upon by human settlements and agricultural land. Let’s hope that development plans are made wisely, so as to preserve the region’s precious biological diversity.
Hadad, E., Weil, G., and M. Charter. 2015. The importance of natural habitats as Short-toed Eagle (Circaetus gallicus) breeding sites. Avian Biology Research 8:160-166.
Photo credits: Short-toed Snake-eagle stamp from Azerbaijan – Colnet.com; Short-toed Snake-eagle print from the Natural History of European Birds, published in Zurich in 1964 – www.etsy.com
Week 2 – 17 July 2016:
The Flexibility of Bird Behaviour
Birds are models of marital bliss. Given that there are something like 10,000 species of birds, it is not surprising that there are plenty of exceptions, but the most common avian breeding system, by far, is monogamy. The specific roles of mother and father offer differ, but in most cases both parents contribute to raising the young. One Mommy, one Daddy, and lots of happy chicks.
If that were the end of the story, it would be a rather boring one, and birds are never boring. The subtle variations on the theme of social monogamy in birds are myriad. One of these variations is interspecific brood parasitism in which females of one species lay their eggs in the nests of birds of another species, leaving the cost of raising their offspring to others. Most bird enthusiasts will be familiar with interspecific brood parasites including Brown-headed Cowbirds in North America, Common Cuckoos in Europe, and Pacific Koel in Australia. Each takes advantage of a wide range of hosts.
Less well known is the phenomenon of conspecific brood parasitism (CBP). In this situation, females lay eggs in the nest of other members of the same species. Birds can be sneaky, and simply detecting CBP is a challenge, so that researchers often rely on genetic mismatches between chicks and their mothers to show that it has happened.
The benefit to the parasite is easy to imagine. A lot of eggs means a lot of hungry chicks. By leaving the eggs with someone else, a female might greatly increase her lifetime reproductive output. In most cases of CBP studied to date, the costs of parasitism to the host have been reasonably small. Ducks and geese provide comparatively little direct care to their young, and a one more chick is unlikely to be costly.
The situation is very different in birds like the Prothonotary Warbler. Breeding in woodlands in the southeastern United States, this warbler nests in natural cavities and nest boxes. As with other songbirds, the young are completely dependent on their parents for care.
Anna Tucker and her colleagues at Virginia Commonwealth University and the College of William and Mary studied conspecific brood parasitism in a population of Prothonotary Warblers near Richmond, Virginia. Many of these birds utilized nest boxes provided by the researchers. Anticipating that CBP would be costly to the individuals whose nests received eggs from other individuals, they compared the reproductive success of hosts to those birds that were not parasitized. Study animals received leg bands for future identification, and had blood samples taken for genetic analysis.
Of 233 broods studied, sixty had one or more chicks that were not the offspring of their social mother. Overall, more than twelve percent of nestlings were parasitic. Not surprisingly, females that had been parasitized by another warbler had more chicks leave the nest, but fledged fewer of their own young than did females who were not parasitized. Being parasitized was costly. Tucker and her coworkers found evidence that at least some of the parasitic females were “floaters,” individuals that had been unable to secure their own nest sites, and so resorted to dumping eggs in the nests of others.
When I contacted her, Tucker explained that one of the most interesting aspects of the ongoing study of Prothonotary Warblers was the effects that the addition of nest boxes has had on the population. “These boxes were first established about 25 years ago to support a then-declining population.” The population has now grown almost to the point of overcrowding. This has probably created the conditions for females to dump eggs. “This flexibility on the part of the females laying parasitic eggs has also reshaped the way I think about avian breeding behaviors,” she wrote. Breeding systems in birds are much more complex that we have considered them to be in the past.
Tucker, A. M., et al. 2016. Opportunistic conspecific brood parasitism in a box-nesting population of Prothonotary Warblers (Protonotaria citrea). Auk 133:29
Photocredits: Prothonotary Warbler stamp, www.canadapost.com; singing Prothonotary Warbler, www.carolinabirdclub.org
Week 1 – 10 July 2016:
Manna from Australia
It seems that Heaven is not the only source of manna. When wounded, some Australian gum trees respond by releasing a syrupy material at the site of the injury. The white gum tree, also known as the manna gum, Eucalyptus viminalis, reacts to damage to its leaves and stems by releasing a sugary fluid that soon crystalizes into a mass that can be eaten by a range of arthropods and a few types of birds. Most of these manna-eating animals are probably opportunists, taking advantage of the yummy treat when they stumble across it. According to recent research by Samuel Case and Amanda Edworthy of the Australian National University in Canberra, Forty-spotted Pardalotes, Pardalotus quadragintus, are an exception. They don’t just harvest manna; these pardalotes mine it.
At one time, the Forty-spotted Pardalote could be found throughout eastern portions of the Australian state of Tasmania. Those days are gone. The bird is a habitat specialist, relying on forests with manna gums. With the clearing of those woodlots, combined with recent drought, the pardalote’s range has contracted to the point where it is now considered an endangered species. If we are to fully understand the decline of the Forty-spotted Pardalote, and perhaps assist in its recovery, we need to understand the relationship between the bird and its habitat.
While studying the breeding biology of Forty-spotted Pardalotes, Case and Edworthy observed these birds using a peculiar notch toward the end of their beaks to make slits in the leaf stalks of mana gum trees. This caused the plants to produce sugary manna. How common is this behaviour, and how important is manna to the lives of the birds?
Between August 2014 and January of 2015, Case and Edworthy made observations of pardalotes in and around nesting sites. They supplemented their direct observations with recordings by digital video cameras placed near nest entrances, capturing images of the food brought to nestlings by their parents. The researchers also became adept at damaging lead stalks artificially to determine what portion of the gum trees produced manna.
More than 80% of the diet of Forty-spotted Pardalote nestlings was manna, supplemented by a few flies and spiders. It has yet to be determined whether manna is rich in amino acids, or if a few arthropods are necessary for a well-balanced diet for the nestlings. Given that manna is chosen as a food for nestlings more often than invertebrates, Case and Edworthy expect that the plant’s exudate provides substantial nutrients.
The findings of Case and Edworthy have profound implications for conservation of the endangered Forty-spotted Pardalote. If captive breeding should ever become necessary, the manna gum will surely be a feature of their enclosure. “All white gum trees may not produce manna equally,” Case explained to me, “and a better understanding of manna production could help to conserve habitat for these endangered birds.”
Are you like me? Are you aching to know what manna tastes like? According to Case, manna “tastes similar to a breath mint.” Now you know.
Case, S. B., and A. B. Edworthy. 2016. First report of ‘mining’ as a feeding behaviour among Australian manna-feeding birds. Ibis 158:407-415.
Photo credits: Forty-spotted Pardalote stamp, www.birdtheme.org; Forty-spotted Pardalote in a manna gum, www.nrmsouth.org.au/forty-spotted-pardalote/