Wednesday, September 28, 2011

Pigeon 'Milk' Contains Antioxidants and Immune-Enhancing Proteins

Pigeon and chick. (Credit: Dr. Tamsyn Crow

ScienceDaily (Sep. 28, 2011) — Production of crop milk, a secretion from the crops of parent birds, is rare among birds and, apart from pigeons, is only found in flamingos and male emperor penguins. Essential for the growth and development of the young pigeon squab, pigeon 'milk' is produced by both parents from fluid-filled cells lining the crop that are rich in fat and protein.

Research published in BioMed Central's open access journal BMC Genomics uses new technology to study the genes and proteins involved in pigeon 'milk' production and shows that pigeon 'milk' contains antioxidants and immune-enhancing proteins.

Researchers from CSIRO Livestock Industries and Deakin University, Australia, compared the global gene expression profiles of the crops of four 'lactating' and four 'non-lactating' female pigeons. As the pigeon genome has not yet been sequenced, they used a chicken microarray to find the genes involved. Genes predominantly over-expressed in 'lactating' birds were those involved in stimulating cell growth, producing antioxidants and in immune response. They also found genes associated with triglyceride fat production, suggesting the fat in the 'milk' is derived from the pigeon's liver.

Lead author, Meagan Gillespie, says, "It is possible that if antioxidant and immune proteins are present in pigeon 'milk', they are directly enhancing the immune system of the developing squab as well as protecting the parental crop tissue." She continues, "This study has provided a snap-shot view of some of the processes occurring when 'lactation' in the pigeon crop is well established. Due to the unusual nature of 'lactation' in the pigeon it would be interesting to investigate the early stages of the differentiation and development of the crop in preparation for 'milk' production to further ascertain gene expression patterns that characterize crop development and 'lactation' in the pigeon."

She concludes, "This mechanism is an interesting example of the evolution of a system with analogies to mammalian lactation, as pigeon 'milk' fulfills a similar function to mammalian milk."

Story Source:
The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by BioMed Central, via EurekAlert!, a service of AAAS.

Journal Reference:
  1. Meagan J. Gillespie, Volker R. Haring, Kenneth A. McColl, Paul Monaghan, John A. Donald, Kevin R. Nicholas, Robert J. Moore, Tamsyn M. Crowley. Histological and global gene expression analysis of the 'lactating' pigeon crop. BMC Genomics, 2011; 12: 452 DOI: 10.1186/1471-2164-12-452

BioMed Central (2011, September 28). Pigeon 'milk' contains antioxidants and immune-enhancing proteins. ScienceDaily. Retrieved September 28, 2011, from­ /releases/2011/09/110919074253.htm

Tuesday, September 27, 2011

Feathered Friends Are Far from Bird-Brained When Building Nests

ScienceDaily (Sep. 26, 2011) — Nest-building is not just instinctive but is a skill that birds learn from experience, research suggests.

Scientists filmed male Southern Masked Weaver birds in Botswana as they built multiple nests out of grass during a breeding season. Their findings contrast with the commonly-held assumption among scientists that nest-building is an innate ability.

The researchers found that individual birds varied their technique from one nest to the next. They also saw that some birds build their nests from left to right, and others from right to left.

Also, as the birds gained more experience in building nests, they dropped blades of grass less often, implying that the art of nest building requires learning.

Researchers from the Universities of Edinburgh, St Andrews and Glasgow together with scientists from Botswana say their findings may help to explain how birds approach nest-building and whether they have the mental capacity to learn, or whether their skills are developed through repetition.

Researchers chose the colourful African bird because they build complex nests, which is potentially a sign of intelligence. More importantly, Weaver birds build many nests -- often dozens in a season, allowing the team to monitor differences in nests built by the same bird.

Dr Patrick Walsh of the University of Edinburgh's School of Biological Sciences, who took part in the study, said: "If birds built their nests according to a genetic template, you would expect all birds to build their nests the same way each time. However this was not the case. Southern Masked Weaver birds displayed strong variations in their approach, revealing a clear role for experience. Even for birds, practice makes perfect."

The research was published in the journal Behavioural Processes and was funded by the Leverhume Trust.

Story Source:
The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by University of Edinburgh, via EurekAlert!, a service of AAAS.

Journal Reference:
  1. Patrick T. Walsh, Mike Hansell, Wendy D. Borello, Susan D. Healy. Individuality in nest building: Do Southern Masked weaver (Ploceus velatus) males vary in their nest-building behaviour? Behavioural Processes, 2011; 88 (1): 1 DOI: 10.1016/j.beproc.2011.06.011

University of Edinburgh (2011, September 26). Feathered friends are far from bird-brained when building nests. ScienceDaily. Retrieved September 27, 2011, from­ /releases/2011/09/110925192704.htm

Thursday, September 22, 2011

Smells may help birds identify their relatives

Researchers at U Chicago and the Chicago Zoological Society found in an experiment at Brookfield Zoo that penguins can recognize the smell of familiar locations, something that may guide them back to their mates. The ability is useful as penguins live in large colonies but remain monogamous. 
Photos by Jim Schulz/Chicago Zoological Society

Smells may help birds identify their relatives

William Harms
Birds may have a more highly developed sense of smell than researchers previously thought, contend scholars who have found that penguins may use smell to determine if they are related to a potential mate.

The research by the University of Chicago and the Chicago Zoological Society, which manages Brookfield Zoo, shows how related birds are able to recognize each other. The study, published Wednesday, Sept. 21 in the article, “Odor-based Recognition of Familiar and Related Conspecifics: A First Test Conducted on Captive Humboldt Penguins (Spheniscus humboldti)” in the journal PLoS ONE, could help conservationists design programs to help preserve endangered species. 

“Smell is likely the primary mechanism for kin recognition to avoid inbreeding within the colony,” said Heather Coffin, lead author of the paper.

Coffin conducted the research while a graduate student at UChicago and was joined in writing the paper by Jill Mateo, associate professor in Comparative Human Development at UChicago, and Jason Watters, director of animal behavior research for the Chicago Zoological Society.

“This is the first study to provide evidence for odor-based kin discrimination in birds,” said Mateo, who is a specialist on kin recognition.

Experts said the work offers important insights into how birds use smell to guide behavior.
“The work by the research group is truly groundbreaking in that it shows for the first time ever in birds how the olfactory sense of captive penguins is both informative and functional in a behaviorally critical context: namely the recognition of friends from foes in general, and relatives from non-relatives in particular,” said Mark E. Hauber, professor of psychology at Hunter College, a specialist on bird social recognition.

Penguins are ideal subjects because they typically live in colonies made up of thousands of birds. They live in monogamous pairs — an arrangement that facilitates rearing of their young, since parents frequently take turns leaving the nest to gather food. Despite the size of the community, mates are able to find each other after traveling for days foraging for food in the ocean.

Research on other sea birds has shown that smell helps guide birds to their home territory and helps them forage for food. Other research has shown that birds could use sound and sight to recognize each other, but no other studies have shown that smell might be used in connection with kin recognition, Mateo said.
In the study conducted at Brookfield Zoo, researchers first sought to determine if the penguins were able to recognize familiar individuals by smell. They constructed an experiment using a dozen penguins, from a group that included breeding pairs, their offspring and nonbreeding individuals. The birds — all Humboldt penguins—endangered natives of Peru—were from groups either on exhibit or off exhibit.

The zoo is an ideal setting for the research, as it has extensive records on which penguins are related and have been housed together, Watters said.

Researchers took odor samples from glands near the penguins’ tails, where an oil that the birds use for preening is secreted. They put the oil on cotton swabs and rubbed the odor inside dog kennels, similar to the enclosures penguins at a zoo use for their nests. They also put the odor on paper coffee filters and placed them under mats inside the kennels.

When the penguins were released to the area containing the kennels, the researchers found that penguins spent more time in the kennels with familiar odors. The penguins were able to distinguish between the odors of birds they spent time with and the odors of unfamiliar penguins.

“What I found particularly notable about the study was that the authors identified the oil secreted from the penguins’ preen gland, which is rubbed on the feathers to make them water repellent, as the odor source used in recognition,” said Bryan D. Neff, professor and associate chairof biology, University of Western Ontario and an expert on kin recognition. “Oils are used in kin recognition by species of other animals, most notably a variety of insect species, including bees and wasps, which when considered with the penguin data provide a wonderful example of convergent evolution.”

“It’s important for birds that live in large groups in the wild, like penguins, to know who their neighbors are so that they can find their nesting areas and also, through experience, know how to get along with the birds nearby,” Watters said.

Because offspring usually return to the same colony for nesting, siblings have the potential of becoming mates, something that can be avoided by their smell mechanism, the new research shows.

Researchers also found that when the birds were exposed to the odors of unfamiliar kin and unfamiliar non-kin, they spent more time in the kennels with odors of unfamiliar non-kin, indicating they were probably able to determine by smell which animals they were related to and were more curious about the novel odors. Being able to make the distinction may help the penguins avoid mating with kin, researchers said.  The discovery also could assist zoos in managing their breeding programs.

“It could also be true that birds do a better job determining who potential mates are than do people in zoos, who spend a great deal of time lining up the appropriate matches,” Watters said.

The ability of birds to be able to recognize familiar scents and thus be guided to their home territory also has potential value to naturalists, he said. “You could imagine that if you were trying to reintroduce birds to an area, you could first treat the area with an odor the birds were familiar with. That would make them more likely to stay.


Wednesday, September 21, 2011

Primitive Birds Shared Dinosaurs' Fate

 The bones are from the 17 species of Cretaceous birds which went extinct around the time of the dinosaurs. The two on the far left are foot bones and the rest are shoulder bones. (Credit: Courtesy Yale University)

ScienceDaily (Sep. 21, 2011) — A new study puts an end to the longstanding debate about how archaic birds went extinct, suggesting they were virtually wiped out by the same meteorite impact that put an end to dinosaurs 65 million years ago.

For decades, scientists have debated whether birds from the Cretaceous period -- which are very different from today's modern bird species -- died out slowly or were killed suddenly by the Chicxulub meteorite. The uncertainty was due in part to the fact that very few fossil birds from the end of this era have been discovered.

Now a team of paleontologists led by Yale researcher Nicholas Longrich has provided clear evidence that many primitive bird species survived right up until the time of the meteorite impact. They identified and dated a large collection of bird fossils representing a range of different species, many of which were alive within 300,000 years of the impact.

"This proves that these species went extinct very abruptly, in terms of geological time scales," said Longrich. The study appears the week of Sept. 19 in the journal Proceedings of the National Academy of Sciences.
The team examined a large collection of about two dozen bird fossils discovered in North America -- representing a wide range of the species that existed during the Cretaceous -- from the collections of Yale's Peabody Museum of Natural History, the American Museum of Natural History, the University of California Museum of Paleontology, and the Royal Saskatchewan Museum. Fossil birds from the Cretaceous are extremely rare, Longrich said, because bird bones are so light and fragile that they are easily damaged or swept away in streams.

"The birds that had been discovered hadn't really been studied in a rigorous way," Longrich said. "We took a much more detailed look at the relationships between these bones and these birds than anyone had done before."

Longrich believes a small fraction of the Cretaceous bird species survived the impact, giving rise to today's birds. The birds he examined showed much more diversity than had yet been seen in birds from the late Cretaceous, ranging in size from that of a starling up to a small goose. Some had long beaks full of teeth.
Yet modern birds are very different from those that existed during the late Cretaceous, Longrich said. For instance, today's birds have developed a much wider range of specialized features and behaviors, from penguins to hummingbirds to flamingoes, while the primitive birds would have occupied a narrower range of ecological niches.

"The basic bird design was in place, but all of the specialized features developed after the mass extinction, when birds sort of re-evolved with all the diversity they display today," Longrich said. "It's similar to what happened with mammals after the age of the dinosaurs."

Longrich adds that this study is not the first to suggest that archaic birds went extinct abruptly. "There's been growing evidence that these birds were wiped out at the same time as the dinosaurs," Longrich said. "But this new evidence effectively closes the book on the debate."

Other authors of the paper include Tim Tokaryk (Royal Saskatchewan Museum) and Daniel Field (Yale University).

Story Source:
The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Yale University.

Journal Reference:
  1. N. R. Longrich, T. Tokaryk, D. J. Field. Mass extinction of birds at the Cretaceous-Paleogene (K-Pg) boundary. Proceedings of the National Academy of Sciences, 2011; 108 (37): 15253 DOI: 10.1073/pnas.1110395108

Yale University (2011, September 21). Primitive birds shared dinosaurs' fate. ScienceDaily. Retrieved September 21, 2011, from­ /releases/2011/09/110919151315.htm

Friday, September 16, 2011

Trapping time in amber

A feather from the late Cretaceous is trapped in amber. 
(Edmonton) Secrets from the age of the dinosaurs are usually revealed by fossilized bones, but a University of Alberta research team has turned up a treasure trove of late Cretaceous feathers, which have been discovered trapped in tree resin.
The resin turned to resilient amber preserving some 80-million-year-old protofeathers, possibly from non-avian dinosaurs, as well as plumage that is very similar to modern birds, including those that can swim under water.

U of A paleontology graduate student Ryan McKellar discovered a wide range of feathers trapped in amber in collections at the Royal Tyrrell Museum and in the private collection of the Leuck family in Medicine Hat.
“Most of the feather specimens were probably blown into contact with the sticky surface of the resin and encapsulated by subsequent resin flows,” said McKellar.
The 11 feather specimens used by the U of A team were all found near the community of Grassy Lake in southern Alberta. The research specimens are described as the richest amber feather find from the late Cretaceous period.

“The amber preserves microscopic detail of the feathers and even their pigment or colour,” said McKellar. “I would describe the colours as typically ranging from brown to black.”
During the late Cretaceous, southern Alberta was a warm coastal region. “The trees that produced the resin were probably comparable to the redwood forests of the Pacific Northwest,” said McKellar.
No dinosaur or avian fossils were found in direct association with the amber feather specimens, but McKellar says comparison between the amber and fossilized feathers found in rock strongly suggest that some of the Grassy Lake specimens are from dinosaurs. The non-avian dinosaur evidence points to small theropods as the source of the feathers.

McKellar says that some of the feather specimens can take on water, enabling the bird to dive more effectively and are very similar to those of modern birds like the Grebe, which are able to swim underwater.
“The preservation of microscopic detail and pigmentation has provided a unique snapshot of feathers and their uses in the late Cretaceous forests of Alberta,” said McKellar.

The U of A team’s research was published Sept. 15, in the journal Science.


Tuesday, September 13, 2011

How penguins find a perfect partner

King penguin parents spend about 14 months incubating their egg, then rearing their chick. They take it in turns to find food, so the strength of their bond is crucial. Biologists want to know how they make this important mate selection, and even how the birds tell a male from a female; the two sexes look almost identical.

Prof Stephen Dobson from the National Centre for Scientific Research in Montpellier, France, playfully sums up his research: "I'm trying to work out what makes a sexy penguin." His studies of the birds on Kerguelen Island have revealed that penguins often struggle to spot a member of the opposite sex.

Prof Dobson also found that males on the island in the Southern Indian Ocean often had to compete particularly hard to snag a female mate. He and his team noticed that, during mating season, trios of penguins would "parade" around together. DNA analysis showed that the trios were usually two males pursuing a female.
When the penguins do find a mate that they take a shine to they carry out an intimate dance – stretching their necks from side to side in what appears to be an elaborate embrace. Occasionally, two males will engage in this mating dance, but the pair usually separate when one finds a female partner.

Prof Dobson’s team, which also includes researchers from the Centre for Functional and Evolutionary Ecology in Montpellier, France, has found that the penguins' bright yellow ear patches play an important role in attraction.

The researchers measured the size and colour intensity of these ear patches to find out how they affect penguin attractiveness. They also used black hair dye to artificially reduce the size of the ear patches.

Males with artificially-reduced ear patches seemed to have less success finding a female. Females also appeared to choose males with larger ear patches, and the researchers think that larger ear patches might convey a male's ability to defend his chick and his territory in the crowded colony.

The scientists hope to unpick the evolutionary mystery of how these birds select a suitable partner who will co-operate in the care of their egg and chick. They also hope to find out more about the penguins' natural behavior to see how they are being affected by environmental change.


Wednesday, September 7, 2011

Macaroni Penguin (Eudyptes chrysolophus): correctly listed as Vulnerable?

BirdLife species factsheet for Macaroni Penguin
Macaroni Penguin Eudyptes chrysolophus breeds in at least 216 colonies at 50 sites in the higher latitudes of the southern hemisphere (Woehler 1993, Woehler and Croxall 1999). The total population is estimated by BirdLife to be c.9 million pairs, although it is argued that this is likely to be an underestimate because of potential underestimates in the South Georgia Island region (USFWS 2008). The species is listed as Vulnerable under criteria A2b,c; A3b,c; A4b,c, on the basis that the global population appears to have declined rapidly, by 30-49% over the preceding three generations, estimated to be c.34 years, and it is projected to decline by 30-49% over the next three generations. As noted in the assessment, however, the current classification is heavily reliant on the extrapolation of small-scale data, thus large-scale surveys are needed to confirm this categorisation.

The current trend estimate is based on recorded local declines. Populations on South Georgia and Bouvet Islands probably increased substantially in the 1960s and 1970s, but have subsequently decreased. Study populations on South Georgia declined by 65% from 1986 to 1998 (J. P. Croxall unpublished data), and the overall South Georgia population probably halved between c.1978 and 1998 (Trathan et al. 1998). Study populations on Marion Island decreased by 50% between 1979 and 1998. In contrast, populations on Kerguelen increased by c.1% per year between 1962 and 1985, and subsequent data from 1998 indicated that the colonies were stable or increasing (H. Weimerskirch per T. Micol in litt. 1999). Populations in South America may be stable, but data are scant.

The validity of the current assessment for this species has been brought into question by a review by the US Fish and Wildlife Services (USFWS 2008). Criticism was levelled at the use of trends at small study colonies to estimate the overall trend for the Prince Edward Islands. Likewise, the conclusion that overall numbers on South Georgia declined by 50% in the last two decades of the 20th century was criticised because it has not been empirically verified in the literature. Although the species is thought to have undergone a recent decline on Bouvet Island, there are apparently no current estimates for the population there. Significant recorded declines in colonies on Marion Island have also been questioned due to changes in survey methodology, and an overall decline of 18% in the island’s estimated total population between 1994-1995 and 2002-2003 is not considered significant by the USFWS (2008) in the context of small fluctuations in the three subsequent three breeding seasons. It has also been asserted that the decline noted on Prince Edward Island between 1976-1977 and 2001-2002, in which the estimated population fell from c.17,000 pairs to c.9,000 pairs (Crawford et al. 2003) was overestimated, and that the overall decline on Marion and Prince Edward Islands combined (c.3.4% of the species’s global population) was 32% between 1979 and 2003 (USFWS 2008).

These criticisms, combined with suggestions that some populations are stable or increasing, or have unknown trends, suggest that the overall estimated rate of decline should be reduced for this species. Comments on the current listing and further information on the species are requested.


Crawford, R. J. M., Cooper, J., Dyer, B. M., Greyling, M., Klages, N. T. W., Ryan, P. G., Petersen, S., Underhill, L. G., Upfold, L., Wilkinson, W., de Villiers, M., du Plessis, S., du Toit, M., Leshoro, T. M. et al. (2003) Populations of surface nesting seabirds at Marion Island, 1994/95-2002/03. Afr. J. Mar. Sci. 25: 427-440.
Trathan, P. N., Croxall, J. P., Murphy, E. J. and Everson, I. (1998) Use of at-sea distribution data to derive potential foraging ranges of macaroni penguins during the breeding season. Mar. Ecol. Prog. Ser. 169: 263-275.
USFWS (2008) Endangered and Threatened Wildlife and Plants; 12-Month Finding on a Petition To List Four Penguin Species as Threatened or Endangered Under the Endangered Species Act and Proposed Rule To List the Southern Rockhopper Penguin in the Campbell Plateau Portion of Its Range. Federal Register, Vol. 73: No. 244.
Woehler, E. J. (1993) The distribution and abundance of Antarctic and Subantarctic penguins. Cambridge, U.K.: Scientific Commission on Antarctic Research.
Woehler, E. J. and Croxall, J. P. (1999) The status and trends of Antarctic and subantarctic seabirds. Mar. Ornithol. 25: 43-66.


Monday, September 5, 2011

ANTARCTICA: Long dives for Emperors

04 September 2011
Issue: 187

Emperor penguins fishing at sea and at an experimental dive hole often spend minimal times on the surface even after dives that last far beyond their measured 5.6 minute aerobic dive limit.

Researchers from the US Scripps Institution of Oceanography and the International Coastal Research Center, Atmosphere and Ocean Research Institute at the University of Tokyo went to the Antarctic and attached accelerometer-based data loggers to Emperor penguins diving in the two different situations to evaluate the capacity of the birds to perform such dives without any apparent prolonged recovery periods.

In a report of the study published in the Journal of Experimental Biology, the researchers say the penguins regularly remain submerged for up to 12 minutes by carefully managing their oxygen reserves.

Lead researcher Paul Ponganis from the Scripps Institution says penguins diving from isolated ice holes fuel the dive aerobically for the first 5.6 minutes and supplement the remainder of the dive with anaerobic metabolism.

But when the researchers compared the aerobic dive limit for ice hole diving penguins with estimates of the aerobic dive limit for freely foraging animals, it appeared the free-ranging birds were able to sustain the aerobic portion of a dive for up to eight minutes. From the data loggers, they could see a surge every time the animal strokes with its wings and they could then count the number of peaks per dive to get the stroke rate pattern.

"We expected that stroke rate would be lower in dives at sea and because of that there would be less muscle work and less oxygen consumption and that would explain how these birds dive as long and as frequently as they do," Ponganis says. But the freely diving birds were stroking faster and were not extending their aerobic dive limit by beating their wings more slowly to conserve oxygen.

When the researchers compared the length of time spent by birds at the surface recovering from dives, the free divers spent no more time at the surface than the ice-hole divers.

Assuming the penguins did not exhale while submerged, they found the penguins carried more air as they extended their dives down to 300 metres, apparently anticipating how deep they would dive and adjusted the amount of air they carried down accordingly.

Yet penguins that dived 400 to 500 metres appeared to be carrying less air than the birds that only dived to 300 metres, leading Ponganis to conclude that they probably exhaled prior to the final segment of the dive.

On one occasion, the researchers recorded a dive where an emperor penguin remained submerged for a record-breaking 27.6 minutes although after it emerged from the water, the bird lay on the ice for six minutes before it stood, took another 20 minutes before it started walking and then waited a further eight hours before going back into the water.

Ponganis says the penguin was exhausted and believes the dive was extended when the pack ice shifted above the penguin's head, blocking its escape route. That it survived is a measure of the bird's remarkable capacity to conserve oxygen under water.