Rethinking the dodo

Researchers are setting out to challenge our misconceptions about the Dodo, one of the most well-known but poorly understood species of bird.

In a paper published today [16 August 2024] in the Zoological Journal of the Linnean Society researchers from the University of Southampton, Natural History Museum (NHM) and Oxford University Museum of Natural History have undertaken the most comprehensive review of the taxonomy of the Dodo and its closest relative, the Rodriguez Island Solitaire.

They've painstakingly gone through 400 years' worth of scientific literature and visited collections around the UK to ensure this iconic species, embodying humanity's destructive potential, is correctly classified.

"The Dodo was the first living thing that was recorded as being present and then disappeared," says Dr Neil Gostling from the University of Southampton, supervising author of the paper. "Before this, it hadn't been thought possible for human beings to influence God's creation in such a way.

"This was a time before the scientific principles and systems we rely on to label and classify a species were in place. Both the Dodo and the Solitaire were gone before we had a chance to understand what we were looking at."

Correcting the record

Much of what was written about the Dodo and the Solitaire was based on accounts from Dutch sailors, representations by artists, and incomplete remains.

The lack of a definitive reference point (type specimen) or convention to label species (zoological nomenclature) led to a series of misidentifications in the centuries following their extinction. New species such as the Nazarene Dodo, the White Dodo, and the White Solitaire were named, but the paper confirms that none of these creatures existed. Still, these erroneous 'pebbles' sent ripples through the waters of zoological literature.

"By the 18th and early 19th centuries, the Dodo and the Solitaire were considered to be mythological beasts," says Dr Mark Young, lead author of the paper from the University of Southampton. "It was the hard work of Victorian-era scientists who finally proved that the Dodo and the Solitaire were not mythological but were giant ground doves."

"Unfortunately, no one could agree how many species there had been," continues Dr Young. "Throughout most of the 19th and 20th centuries, researchers thought there were three different species, although some people thought there had been four or even five different species."

To unpick this confusion, researchers went through all the literature on the Dodo and Rodriguez Solitaire encompassing hundreds of accounts dating back to 1598 and visited specimens around the UK, including the world's only surviving soft tissue from the Dodo, in the Oxford Museum.

"More has been written about the Dodo than any other bird, yet virtually nothing is known about it in life," says Dr Julian Hume, an avian palaeontologist at the Natural History Museum and coauthor of the paper.

"Based on centuries of nomenclatural confusion, and some 400 years after its extinction, the Dodo and Solitaire, continue to prompt heated debate. We've gone from where the first statements were made, seen how these have developed, and identified various rabbit holes to correct the record, as best we can."

Through this work, researchers were able to confirm that both birds were members of the columbid (pigeon and dove) family.

"Understanding its wider relationships with other pigeons is of taxonomic importance, but from the perspective of conservation, the loss of the dodo and the solitaire a few decades later means a unique branch of the pigeon family tree was lost," says Dr Gostling. "There are no other birds alive today like these two species of giant ground dove."

Challenging our misconceptions

The researchers believe the popular idea of the Dodo as a fat, slow animal, predestined for extinction is flawed.

"Even four centuries later, we have so much to learn about these remarkable birds," says Dr Young. "Was the Dodo really the dumb, slow animal we've been brought up to believe it was? The few written accounts of live Dodos say it was a fast-moving animal that loved the forest."

Dr Gostling adds: "Evidence from bone specimens suggests that the Dodo's tendon which closed its toes was exceptionally powerful, analogous to climbing and running birds alive today. The dodo was almost certainly a very active, very fast animal.

"These creatures were perfectly adapted to their environment, but the islands they lived on lacked mammalian predators. So, when humans arrived, bringing rats, cats, and pigs, the Dodo and the Solitaire never stood a chance.

"Dodos held an integral place in their ecosystems. If we understand them, we might be able to support ecosystem recovery in Mauritius, perhaps starting to undo the damage that began with the arrival of humans nearly half a millennium ago."

Learning 'valuable lessons'

The study marks the beginning of a wider project to understand the biology of these iconic animals.

"The mystery of the Dodo bird is about to be cracked wide open," says Dr Markus Heller, Professor of Biomechanics at the University of Southampton, a coauthor on the paper.

"We have assembled a fantastic team of scientists to uncover the true nature of this famous extinct bird. But we are not just looking back in time -- our research could help save today's endangered birds too."

Dr Heller explains: "Using cutting-edge computer technology, we are piecing together how the Dodo lived and moved. This isn't just about satisfying our curiosity. By understanding how birds evolved in the past, we are learning valuable lessons that could help protect bird species today."

"It's like solving a 300-year-old puzzle, and the solution might just help us prevent more birds from going the way of the Dodo."

The project will include work with palaeoartist Karen Fawcett, who has created a detailed, life-size model of the Dodo to bring the words on the pages of books and journal articles to life. She says: "This work has been the merging of science and art to achieve accuracy and realism so that these creatures come back from the dead, real and tangible for people to touch and see."

Read more at Science Daily

Fossil shows how penguins' wings evolved

A tiny fossil penguin plays a huge role in the evolutionary history of the bird, an international study shows.

Published in the Journal of the Royal Society of New Zealand, the study describes a new species of fossil penguin which lived in Otago about 24 million years ago.

Named Pakudyptes hakataramea, the penguin was very small -- about the same size as the little blue penguin, the smallest in the world -- with anatomical adaptations that allowed it to dive.

Lead author Dr Tatsuro Ando, formerly a PhD candidate at the University of Otago -- Ōtākou Whakaihu Waka and now at the Ashoro Museum of Palentology in Japan, collaborated with researchers from Otago, Okayama University of Science and Osaka University.

Dr Ando's inspiration for the paper came from discussions with the late Professor Ewan Fordyce, his supervisor and mentor at Otago.

Researchers analysed three bones -- a humerus, femur and ulna -- found by Professor Fordyce in the Hakataramea Valley, South Canterbury.

Dr Ando says Pakudyptes fills a morphological gap between modern and fossil penguins.

"In particular, the shape of the wing bones differed greatly, and the process by which penguin wings came to have their present form and function remained unclear," he says.

The humerus and ulna highlight how penguins' wings have evolved.

"Surprisingly, while the shoulder joints of the wing of Pakudyptes were very close to the condition of the present-day penguin, the elbow joints were very similar to those of older types of fossil penguins.

"Pakudyptes is the first fossil penguin ever found with this combination, and it is the 'key' fossil to unlocking the evolution of penguin wings."

Co-author Dr Carolina Loch, from Otago's Faculty of Dentistry, says analysis of the internal bone structure conducted at the Faculty of Dentistry, with comparison with data on living penguins provided from the Okayama University of Science, shows these penguins had microanatomical features suggestive of diving.

Modern penguins have excellent swimming abilities, largely due to their dense, thick bones that contribute to buoyancy during diving.

In Pakudyptes, the bone cortex was reasonably thick although the medullary cavity, which contains bone marrow, was open, similar to what we see in the modern little blue penguin, which tends to swim in shallow waters.

The ability for Pakudyptes to dive and swim comes down to the distinctive combination of its bones.

Bones such as the humerus and ulna show areas for attachment of muscles and ligaments which reveal how the wings were being used to swim and manoeuvre under water.

Read more at Science Daily

How do birds flock? Researchers do the math to reveal previously unknown aerodynamic phenomenon

In looking up at the sky during these early weeks of spring, you may very well see a flock of birds moving in unison as they migrate north. But how do these creatures fly in such a coordinated and seemingly effortless fashion?

Part of the answer lies in precise, and previously unknown, aerodynamic interactions, reports a team of mathematicians in a newly published study. Its breakthrough broadens our understanding of wildlife, including fish, who move in schools, and could have applications in transportation and energy.

"This area of research is important since animals are known to take advantage of the flows, such as of air or water, left by other members of a group to save on the energy needed to move or to reduce drag or resistance," explains Leif Ristroph, an associate professor at New York University's Courant Institute of Mathematical Sciences and the senior author of the paper, which appears in the journal Nature Communications. "Our work may also have applications in transportation -- like efficient propulsion through air or water -- and energy, such as more effectively harvesting power from wind, water currents, or waves."

The team's results show that the impact of aerodynamics depends on the size of the flying group -- benefiting small groups and disrupting large ones.

"The aerodynamic interactions in small bird flocks help each member to hold a certain special position relative to their leading neighbor, but larger groups are disrupted by an effect that dislodges members from these positions and may cause collisions," notes Sophie Ramananarivo, an assistant professor at École Polytechnique Paris and one of the paper's authors.

Previously, Ristroph and his colleagues uncovered how birds move in groups -- but these findings were drawn from experiments mimicking the interactions of two birds. The new Nature Communications research expanded the inquiry to account for many flyers.

To replicate the columnar formations of birds, in which they line up one directly behind the other, the researchers created mechanized flappers that act like birds' wings. The wings were 3D-printed from plastic and driven by motors to flap in water, which replicated how air flows around bird wings during flight. This "mock flock" propelled through water and could freely arrange itself within a line or queue, as seen in a video of the experiment.

The flows affected group organization in different ways -- depending on the size of the group.

For small groups of up to about four flyers, the researchers discovered an effect by which each member gets help from the aerodynamic interactions in holding its position relative to its neighbors.

"If a flyer is displaced from its position, the vortices or swirls of flow left by the leading neighbor help to push the follower back into place and hold it there," explains Ristroph, director of NYU's Applied Mathematics Laboratory, where the experiments were conducted. "This means the flyers can assemble into an orderly queue of regular spacing automatically and with no extra effort, since the physics does all the work.

"For larger groups, however, these flow interactions cause later members to be jostled around and thrown out of position, typically causing a breakdown of the flock due to collisions among members. This means that the very long groups seen in some types of birds are not at all easy to form, and the later members likely have to constantly work to hold their positions and avoid crashing into their neighbors."

The authors then deployed mathematical modeling to better understand the underlying forces driving the experimental results.

Here, they concluded that flow-mediated interactions between neighbors are, in effect, spring-like forces that hold each member in place -- just as if the cars of a train were connected by springs.

However, these "springs" act in only one direction -- a lead bird can exert force on its follower, but not vice versa -- and this non-reciprocal interaction means that later members tend to resonate or oscillate wildly.

"The oscillations look like waves that jiggle the members forwards and backwards and which travel down the group and increase in intensity, causing later members to crash together," explains Joel Newbolt, who was an NYU graduate student in physics at the time of research.

The team named these new types of waves "flonons," which is based on the similar concept of phonons that refer to vibrational waves in systems of masses linked by springs and which are used to model the motions of atoms or molecules in crystals or other materials.

"Our findings therefore raise some interesting connections to material physics in which birds in an orderly flock are analogous to atoms in a regular crystal," Newbolt adds.

Read more at Science Daily

Africa's iconic flamingos threatened by rising lake levels

It is one of the world's most spectacular sights -- huge flocks or "flamboyances" of flamingos around East Africa's lakes -- as seen in the film Out of Africa or David Attenborough's A Perfect Planet.

But new research led by King's College London has revealed how the lesser flamingo is at danger of being flushed out of its historic feeding grounds, with serious consequences for the future of the species.

For the first time satellite earth observation data has been used to study all the key flamingo feeding lakes in Ethiopia, Kenya and Tanzania over two decades and it identified how rising water levels are reducing the birds' main food source.

The authors warn the birds are likely to be pushed into new unprotected areas in the search for food, especially given predicted higher levels of rainfall linked to climate change.

They are now calling for coordinated conservation action across international borders, improved monitoring and more sustainable management of land surrounding important flamingo lakes.

Lead author Aidan Byrne, a PhD student jointly supervised by King's College London and the Natural History Museum, said the region was home to more than three quarters of the global population of lesser flamingos, but their numbers are declining.

"Lesser flamingos in East Africa are increasingly vulnerable, particularly with increased rainfall predicted for the region under climate change. Without improved lake monitoring and catchment management practices, the highly specialised species found in soda lake ecosystems -- including lesser flamingos -- could be lost," he said.

The study, published in the journal Current Biology, is the first in which satellite earth observation data has been used to study all 22 key flamingo feeding soda lakes in East Africa. This analysis was combined with climate records and bird observation data over more than two decades.

By studying on this large scale, for the first time researchers were able to see changing food availability across the whole network of lakes, including significant declines in recent years, and how bird numbers decreased as lake surface area increased. They also identified the lakes the birds might move to in the future.

Co-author, Dr Emma Tebbs, from King's College London said whilst flamingos naturally travel in search of food, the degradation of their historic feeding and breeding sites was a serious concern.

"East African populations could potentially move north or south away from the equator in search of food resources. And whilst six study lakes increased in habitat suitability from 2010 to 2022, only three of those have some level of conservation protection.

"Increases in water levels could lead to lesser flamingos becoming more reliant on lakes that are unprotected, outside of current nature reserves and protected sites, which has implications for conservation and ecotourism revenues."

Soda lakes are some of the harshest environments on Earth, being both highly saline and very alkaline. Despite this, many species have evolved to thrive in these conditions, including the flamingo and its phytoplankton prey, which they filter from the water using their sieve-like beaks.

The research found rising water levels across the region's soda lakes were diluting their normally salty and alkaline nature, leading to a decline in populations of phytoplankton, which was measured by the amount of a photosynthetic pigment called chlorophyll-a present in the lakes.

The team found that phytoplankton levels have been declining over the 23 years of study and linked this to increases in the surface areas of the lakes over the same period.

The largest losses in phytoplankton biomass occurred in the equatorial Kenyan lakes, notably at the important tourist lakes Bogoria, Nakuru and Elmenteita, and in the northern Tanzanian lakes that saw the largest increases in surface area.

Nakuru is one of the most important flamingo feeding lakes in East Africa, historically supporting over one million birds at a time. The lake increased in surface area by 91% from 2009 to 2022 whilst its mean chlorophyll-a concentrations halved.

Natron in Tanzania is the only regular breeding site for lesser flamingos in East Africa and it has experienced declining productivity alongside rising water levels in recent years. If phytoplankton biomass continues to decline there and at other nearby feeding lakes, it will no longer be a suitable breeding site.

Read more at Science Daily

Fossil named 'Attenborough's strange bird' was the first in its kind without teeth

A new fossil, named "Attenborough's strange bird" after naturalist and documentarian Sir David Attenborough, is the first of its kind to evolve a toothless beak. It's from a branch of the bird family tree that went extinct in the mass extinction 66 million years ago, and this strange bird is another puzzle piece that helps explain why some birds -- and their fellow dinosaurs -- went extinct, and others survived to today.

No birds alive today have teeth. But that wasn't always the case -- many early fossil birds had beaks full of sharp, tiny teeth. In a paper in the journal Cretaceous Research, scientists have described a new species of fossil bird that was the first of its kind to evolve toothless-ness; its name, in honor of naturalist Sir David Attenborough, means "Attenborough's strange bird."

"It is a great honour to have one's name attached to a fossil, particularly one as spectacular and important as this. It seems the history of birds is more complex than we knew," says Sir David Attenborough.

All birds are dinosaurs, but not all dinosaurs fall into the specialized type of dinosaurs known as birds, sort of like how all squares are rectangles, but not all rectangles are squares. The newly described Imparavis attenboroughi is a bird, and therefore, also a dinosaur.

Imparavis attenboroughi was a member of a group of birds called enantiornithines, or "opposite birds," named for a feature in their shoulder joints that is "opposite" from what's seen in modern birds. Enantiornithines were once the most diverse group of birds, but they went extinct 66 million years ago following the meteor impact that killed most of the dinosaurs. Scientists are still working to figure out why the enantiornithines went extinct and the ornithuromorphs, the group that gave rise to modern birds, survived.

"Enantiornithines are very weird. Most of them had teeth and still had clawed digits. If you were to go back in time 120 million years in northeastern China and walk around, you might have seen something that looked like a robin or a cardinal, but then it would open its mouth, and it would be filled with teeth, and it would raise its wing, and you would realize that it had little fingers," says Alex Clark, a PhD student at the University of Chicago and the Field Museum and the paper's corresponding author.

But "Attenborough's strange bird" bucked this trend. "Scientists previously thought that the first record of toothlessness in this group was about 72 million years ago, in the late Cretaceous. This little guy, Imparavis, pushes that back by about 48 to 50 million years. So toothlessness, or edentulism, evolved much earlier in this group than we thought," says Clark.

The specimen was found by an amateur fossil collector near the village of Toudaoyingzi in northeastern China and donated to the Shandong Tianyu Museum of Nature. Clark's advisor and co-author on the paper, Field Museum associate curator of fossil reptiles Jingmai O'Connor, first noticed something unusual about this fossil several years ago, when she was visiting the Shandong Tianyu Museum's collections.

"I think what drew me to the specimen wasn't its lack of teeth -- it was its forelimbs," says O'Connor. "It had a giant bicipital crest -- a bony process jutting out at the top of the upper arm bone, where muscles attach. I'd seen crests like that in Late Cretaceous birds, but not in the Early Cretaceous like this one. That's when I first suspected it might be a new species."

O'Connor, Clark, and their coauthors in China, Xiaoli Wang, Xiangyu Zhang, Xing Wang, Xiaoting Zheng, and Zhonghe Zhou, undertook further study of the specimen and determined that it did indeed represent an animal new to science.

The unusual wing bones could have allowed for muscle attachments that let this bird flap its wings with extra power. "We're potentially looking at really strong wing beats. Some features of the bones resemble those of modern birds like puffins or murres, which can flap crazy fast, or quails and pheasants, which are stout little birds but produce enough power to launch nearly vertically at a moment's notice when threatened," says Clark.

Meanwhile, the bird's toothless beak doesn't necessarily tell scientists what it was eating, since modern toothless birds have a wide variety of diets. Like its fellow enantiornithines, and unlike modern birds, it does not appear to have a digestive organ called a gizzard, or gastric mill, that helped it crush up its food.

While Clark notes that "an animal is more than the sum of its parts, and we can't fully know what an animal's life was like just by looking at single components of its body," he and his coauthors have been able to hypothesize about some of Imparavis's behavior and ecology, based on the details of its wings, feet, and beak together. "I like to think of these guys kind of acting like modern robins. They can perch in trees just fine, but for the most part, you see them foraging on the ground, hopping around and walking," says Clark.

"It seems like most enantiornithines were pretty arboreal, but the differences in the forelimb structure of Imparavis suggests that even though it's still probably lived in the trees, it maybe ventured down to the ground to feed, and that might mean it had a unique diet compared to other enantiornithines, which also might explain why it lost its teeth," says O'Connor.

In the paper, the researchers also revisited a previously described fossil bird, Chiappeavis (which O'Connor named eight years ago after her PhD advisor), and suggest that it too was an early toothless enantiornithine. This finding, along with Imparavis, indicates that toothlessness may not have been quite as unique in Early Cretaceous enantiornithines as previously thought.

Clark said that nature documentaries by Sir David Attenborough, in which the renowned British naturalist narrates the behavior of different animals, were pivotal to his own interest in science. "I most likely wouldn't be in the natural sciences if it weren't for David Attenborough's documentaries," says Clark, explaining why he chose to name the new fossil after Attenborough.

Clark and O'Connor noted the importance of Attenborough's messaging that not only celebrates life on earth, but also warns against the mass extinction the planet is undergoing due to human-caused climate change and habitat destruction.

Read more at Science Daily

Pacific kelp forests are far older that we thought

The unique underwater kelp forests that line the Pacific Coast support a varied ecosystem that was thought to have evolved along with the kelp over the past 14 million years.

But a new study shows that kelp flourished off the Northwest Coast more than 32 million years ago, long before the appearance of modern groups of marine mammals, sea urchins, birds and bivalves that today call the forests home.

The much greater age of these coastal kelp forests, which today are a rich ecosystem supporting otters, sea lions, seals, and many birds, fish and crustaceans, means that they likely were a main source of food for an ancient, now-extinct mammal called a desmostylian. The hippopotamus-sized grazer is thought to be related to today's sea cows, manatees and their terrestrial relatives, the elephants.

"People initially said, "We don't think the kelps were there before 14 million years ago because the organisms associated with the modern kelp forest were not there yet,'" said paleobotanist Cindy Looy, professor of integrative biology at the University of California, Berkeley. "Now, we show the kelps were there, it's just that all the organisms that you expect to be associated with them were not. Which is not that strange, because you first need the foundation for the whole system before everything else can show up."

Evidence for the greater antiquity of kelp forests, reported this week in the journal Proceedings of the National Academy of Sciences, comes from newly discovered fossils of the kelp's holdfast -- the root-like part of the kelp that anchors it to rocks or rock-bound organisms on the seafloor. The stipe, or stem, attaches to the holdfast and supports the blades, which typically float in the water, thanks to air bladders.

Looy's colleague, Steffen Kiel, dated these fossilized holdfasts, which still grasp clams and envelop barnacles and snails, to 32.1 million years ago, in the middle of the Cenozoic Era, which stretches from 66 million years ago to the present. The oldest previously known kelp fossil, consisting of one air bladder and a blade similar to that of today's bull kelp, dates from 14 million years ago and is in the collection of the University of California Museum of Paleontology (UCMP).

"Our holdfasts provide good evidence for kelp being the food source for an enigmatic group of marine mammals, the desmostylia," said Kiel, lead author of the paper and a senior curator at the Swedish Museum of Natural History in Stockholm. "This is the only order of Cenozoic mammals that actually went extinct during the Cenozoic. Kelp had long been suggested as a food source for these hippo-sized marine mammals, but actual evidence was lacking. Our holdfasts indicate that kelp is a likely candidate."

According to Kiel and Looy, who is the senior author of the paper and UCMP curator of paleobotany, these early kelp forests were likely not as complex as the forests that evolved by about 14 million years ago. Fossils from the late Cenozoic along the Pacific Coast indicate an abundance of bivalves -- clams, oysters and mussels -- birds and sea mammals, including sirenians related to manatees and extinct, bear-like predecessors of the sea otter, called Kolponomos. Such diversity is not found in the fossil record from 32 million years ago.

"Another implication is that the fossil record has, once again, shown that the evolution of life -- in this case, of kelp forests -- was more complex than estimated from biological data alone," Kiel said. "The fossil record shows that numerous animals appeared in, and disappeared from, kelp forests during the past 32 million years, and that the kelp forest ecosystems that we know today have only evolved during the past few million years."

The value of fossil hunting amateurs

The fossils were discovered by James Goedert, an amateur fossil collector who has worked with Kiel in the past. When Goedert broke open four stone nodules he found along the beach near Jansen Creek on the Olympic Peninsula in Washington, he saw what looked like the holdfasts of kelp and other macroalgae common along the coast today.

Kiel, who specializes in invertebrate evolution, agreed and subsequently dated the rocks based on the ratio of strontium isotopes. He also analyzed oxygen isotope levels in the bivalve shells to determine that the holdfasts lived in slightly warmer water than today, at the upper range of temperatures found in modern kelp forests.

Looy reached out to co-author Dula Parkinson, a staff scientist with the Advanced Light Source at Lawrence Berkeley National Laboratory, for help obtaining a 3D X-ray scan of one of the holdfast fossils using Synchrotron Radiation X-ray Tomographic Microscopy (SRXTM). When she reviewed the detailed X-ray slices through the fossil, she was amazed to see a barnacle, a snail, a mussel and tiny, single-celled foraminifera hidden within the holdfast, in addition to the bivalve on which it sat.

Looy noted, however, that the diversity of invertebrates found within the 32-million-year-old fossilized holdfast was not as high as would be found inside a kelp holdfast today.

"The holdfasts are definitely not as rich as they would be if you would go to a kelp ecosystem right now," Looy said. "The diversifying of organisms living in these ecosystems hadn't started yet."

Kiel and Looy plan further studies of the fossils to see what they reveal about the evolution of the kelp ecosystem in the North Pacific and how that relates to changes in the ocean-climate system.

Read more at Science Daily

Oldest known fossilized skin is 21 million years older than previous examples

Researchers have identified a 3D fragment of fossilized skin that is at least 21 million years than previously described skin fossils. The skin, which belonged to an early species of Paleozoic reptile, has a pebbled surface and most closely resembles crocodile skin. It's the oldest example of preserved epidermis, the outermost layer of skin in terrestrial reptiles, birds, and mammals, which was an important evolutionary adaptation in the transition to life on land. The fossil is described on January 11 in the journal Current Biology along with several other specimens that were collected from the Richards Spur limestone cave system in Oklahoma.

"Every now and then we get an exceptional opportunity to glimpse back into deep time," says first author Ethan Mooney, a paleontology graduate student at the University of Toronto who worked on the project as an undergraduate with paleontologist Robert Reisz at the University of Toronto.

"These types of discoveries can really enrich our understanding and perception of these pioneering animals."

Skin and other soft tissues are rarely fossilized, but the researchers think that skin preservation was possible in this case because of the cave system's unique features, which included fine clay sediments that slowed decomposition, oil seepage, and a cave environment that was likely an oxygenless environment.

"Animals would have fallen into this cave system during the early Permian and been buried in very fine clay sediments that delayed the decay process," says Mooney.

"But the kicker is that this cave system was also an active oil seepage site during the Permian, and interactions between hydrocarbons in petroleum and tar are likely what allowed this skin to be preserved."

The skin fossil is tiny -- smaller than a fingernail. Microscopic examination undertaken by coauthor Tea Maho of the University of Toronto Mississauga revealed epidermal tissues, a hallmark of the skin of amniotes, the terrestrial vertebrate group that includes reptiles, birds, and mammals and which evolved from amphibian ancestors during the Carboniferous Period.

"We were totally shocked by what we saw because it's completely unlike anything we would have expected," says Mooney.

"Finding such an old skin fossil is an exceptional opportunity to peer into the past and see what the skin of some of these earliest animals may have looked like."

The skin shares features with ancient and extant reptiles, including a pebbled surface similar to crocodile skin, and hinged regions between epidermal scales that resemble skin structures in snakes and worm lizards.

However, because the skin fossil is not associated with a skeleton or any other remains, it is not possible to identify what species of animal or body region the skin belonged to.

The fact that this ancient skin resembles the skin of reptiles alive today shows how important these structures are for survival in terrestrial environments.

"The epidermis was a critical feature for vertebrate survival on land," says Mooney.

"It's a crucial barrier between the internal body processes and the harsh outer environment."

The researchers say that this skin may represent the ancestral skin structure for terrestrial vertebrates in early amniotes that allowed for the eventual evolution of bird feathers and mammalian hair follicles.

Read more at Science Daily

Extremely rare bird captured on film

A striking and extremely rare half female, half male bird has been spotted by a University of Otago zoologist.

Sesquicentennial Distinguished Professor Hamish Spencer was holidaying in Colombia when an amateur ornithologist John Murillo pointed out a wild Green Honeycreeper with distinct half green, or female, and half blue, male, plumage.

"Many birdwatchers could go their whole lives and not see a bilateral gynandromorph in any species of bird. The phenomenon is extremely rare in birds, I know of no examples from New Zealand ever.

"It is very striking, I was very privileged to see it," Professor Spencer says.

Photographs of the bird make the discovery even more significant as they are "arguably the best of a wild bilateral gynandromorphic bird of any species ever."

A report on the find, only the second recorded example of gynandromorphism in the species in more than 100 years, has just been published in the Journal of Field Ornithology.

Professor Spencer says gynandromorphs -- animals with both male and female characteristics in a species that usually have separate sexes -- are important for our understanding of sex determination and sexual behaviour in birds.

The main groups in which the phenomenon has been recorded include animal species which feature strong sexual dimorphism; most often insects, especially butterflies, crustaceans, spiders, even lizards and rodents.

"This particular example of bilateral gynandromorphy -- male one side and female the other -- shows that, as in several other species, either side of the bird can be male or female.

"The phenomenon arises from an error during female cell division to produce an egg, followed by double-fertilization by two sperm," he explains.

He hopes the novel discovery will inspire people to "treasure exceptions" as they always reveal something interesting.

Read more at Science Daily

Birds set foot near South Pole in Early Cretaceous, Australian tracks show

The discovery of 27 avian footprints on the southern Australia coast -- dating back to the Early Cretaceous when Australia was still connected to Antarctica -- opens another window onto early avian evolution and possible migratory behavior.

PLOS ONE published the discovery of some of the oldest, positively identified bird tracks in the Southern Hemisphere, dated to between 120 million and 128 million years ago.

"Most of the bird tracks and body fossils dating as far back as the Early Cretaceous are from the Northern Hemisphere, particularly from Asia," says Anthony Martin, first author of the study and a professor in Emory University's Department of Environmental Sciences. "Our discovery shows that there were many birds, and a variety of them, near the South Pole about 125 million years ago."

Martin is a geologist and paleontologist focused primarily on ichnology -- the study of traces of life such as tracks, burrows, nests and tooth marks.

The international team of co-authors also includes researchers from Monash University and the Museums Victoria Research Institute in Australia; the Benemérita Normal School of Coahuila in Mexico and the Smithsonian Institution.

A possible migratory route

The 27 bird tracks vary in form and size and are among the largest known from the Early Cretaceous. They range from seven to 14 centimeters wide, which is similar to tracks of modern-day shorebirds, such as small herons and oystercatchers.

The tracks were found in the Wonthaggi Formation south of Melbourne. The rocky coastal strata mark where the ancient supercontinent Gondwana began to break up around 100 million years ago when Australia separated from Antarctica.

The polar environment at that time was a rift valley with braided rivers. Although the mean annual air temperature was higher during the Cretaceous than today, during the polar winters the ecosystem experienced deep, freezing temperatures and months of darkness.

The Wonthaggi avian tracks occurred on multiple stratigraphic levels, indicating a recurrent presence of a variety of birds. It also suggests seasonal formation of the tracks during polar summers, perhaps on a migratory route.

"The birds would likely have been stepping on soft sand or mud," Martin says. "Then the tracks may have been buried by a gentle river flow that deposited more sand or mud on top of them."

A scarcity of bird fossils

The Wonthaggi Formation is famous for its variety of polar dinosaur bones, although bird-fossil finds are extremely rare. The Cretaceous strata of the formation has yielded only one tiny bird bone -- a wishbone -- and a few feathers.

"Birds have such thin and tiny bones," Martin says. "Think of the likelihood of a sparrow being preserved in the geologic record as opposed to an elephant."

Birds are also lightweight and don't leave much of a foot impression, he adds.

Martin and colleagues discovered two 105-million-year-old bird tracks in Australia's Eumeralla Formation in 2013, making them the oldest from Australia at the time.

An eagle eye

Co-author Melissa Lowery, a local volunteer fossil hunter, first spotted some of the tracks in the current discovery in 2020. Dubbed "the doyenne of dinosaur discovery," Lowery has found hundreds of bones and more than 100 dinosaur footprints.

"Melissa is incredibly skilled at finding fossil tracks," Martin says. "Some of these tracks are subtle even for me, and I have lots of experience and training."

Most of the tracks were only exposed at low tide and some of them were encrusted by marine life such as algae, barnacles and mollusks.

Due to international travel restrictions in Australia during the COVID-19 pandemic, Martin had to wait until 2022 before he could travel to the site to lead the analyses of the tracks.

He was joined in the field by co-authors Patricia Vickers-Rich, professor of paleontology at Monash University, and Thomas Rich, curator of vertebrate aleontology at Museums Victoria Research Institute. The couple have led a major effort since the 1970s to uncover fossils in the Australian state of Victoria and to interpret the biota of Gondwana.

Also assisting in the field analyses were co-authors Mike Hall, a geologist at Monash University, and Peter Swinkels, a taxidermist at Museums Victoria Research Institute and an expert at preserving specimens through moldings and casts.

The thinness of the toes relative to the track lengths, the wide angles between the toes and the thin sharp claws and rear toes on some of the tracks helped Martin to verify their avian identity.

Co-author Claudia Serrano-Brañas, a paleontologist at the Benemérita Normal School of Coahuila and the National Museum of Natural History, Smithsonian Institution, verified similarities between the Australian bird footprints and ancient bird footprints from other parts of the world.

Swinkels created resin casts of the Australian tracks that brought into greater relief some of the nuances of the impressions. The casts provide a tool for further study. They also serve to preserve the finds. The silty, sandstone beds containing the footprints are rapidly eroding under the coastal tides and waves.

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Temperature variability reduces nesting success

Many songbirds are nesting earlier in spring because of warmer temperatures brought about by climate change. But the shift brings another danger that is especially deadly for nestlings: greater exposure to temperature variability in the form of cold snaps and heat waves. Such extremes result in more nest failures. These findings come from a Cornell Lab of Ornithology study just published in the journal Nature Communications.

"When we talk about temperature changes, the focus is mostly on averages," said co-lead author Conor Taff, a researcher in Cornell University's Ecology and Evolutionary Biology Department. "But all creatures, including humans, interact with weather conditions right in the moment, not with long-term averages. Even a one or two-day period when it's really cold or really hot can be incredibly challenging even if the average temperature hasn't changed. Changing temperature averages and temperature variability are two different components of climate change."

To understand how temperature variability might affect nesting success, the researchers analyzed 300,000 breeding bird records submitted to the Cornell Lab's NestWatch project between 1995 and 2020. They pinpointed the coldest three-day day period and the hottest three-day period for each one of the nests and then looked at whether those values predicted lower nesting success. Success was measured by how many nestlings survived to fledge.

"We found that 16 of the 24 species we studied had reduced reproductive success when a cold snap occurred during the incubation or nestling stages," Taff said. "Eleven of 24 had reduced success when a heat wave occurred during the breeding season. Aerial insectivores were the most sensitive to temperature extremes, especially cold."

The vast majority of birds feed insects to their young, regardless of their final diet, and cold snaps reduce insect availability. If these episodes occur when nestlings are most vulnerable, they can trigger a mass die-off. During a cold snap, adult birds may move away to find survivable conditions which leaves eggs and nestlings exposed to cold and lack of food.

"It's the nestlings that really get hit hard because they can't regulate their own body temperature yet," said co-author Ryan Shipley, a Cornell University Ph.D. student at the time of the research. "Nestlings also grow at an exponential rate during the first week or two of life and if insect activity drops because of a cold snap, the young birds likely won't survive."

Taff and Shipley also examined 100 years of weather data to see if there have been changes in the timing of cold snaps and heat waves during the March through August breeding season in the United States and Canada. Although they found no clear pattern in the timing of temperature extremes, they do note that it's getting warmer everywhere.

"Even if nestlings somehow manage to survive a cold snap or heat wave, there may still be long-term consequences affecting the overall health of the birds," notes Shipley. "We're only looking at a brief snapshot during early life and cannot measure long-term health in an unbanded wild population."

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Cracking the code: Genome sequencing reveals why songbirds are larger in colder climates

Scientists have unlocked the genetic basis underlying the remarkable variation in body size observed in song sparrows, one of North America's most familiar and beloved songbirds. This discovery also provides insights into this species' capacity to adapt to the challenges of climate change.

The study, published today in Nature Communications, used genomic sequencing to successfully pinpoint eight genetic variants, or DNA mutations, largely responsible for the nearly threefold difference in body size observed across the song sparrow range from Mexico to Alaska. For instance, song sparrows that live year-round in the Aleutian Islands can be up to three times larger than their counterparts in the coastal marshes of California.

Katherine Carbeck, the study's first author and a PhD candidate in the faculty of forestry, University of British Columbia, explains that body size varies predictably in many species that inhabit vastly different climatic conditions, aligning with "Bergmann's rule" which states that organisms in cooler climates tend to be larger as an adaptation to regulate body temperature.

"The existence of 'locally adapted' populations implies that natural selection has shaped the genetic makeup of song sparrow populations across their range, enabling individuals to survive and reproduce in drastically different climatic conditions," said Carbeck. "However, the genetic mechanisms underlying Bergmann's rule have remained elusive until now."

Whole-genome sequencing cracks the code

Carbeck and colleagues from the Cornell Lab of Ornithology, University of Alaska and Ouachita Baptist University used the power of whole-genome sequencing to decode the entire song sparrow genome and unlock its secrets.

They combed through genetic samples from the two largest song sparrow subspecies that live year-round in the Aleutian Islands, as well as two smaller subspecies: one that breeds in Alaska but migrates to warmer sites in winter, and one that lives year-round on the B.C. coast, where the Pacific Ocean maintains comparatively mild winter weather.

Their comparison of the larger and smaller-bodied subspecies revealed several candidate genes associated with body mass. By characterizing these candidates, they identified eight specific genetic variants closely linked to body mass -- aligning with Bergmann's rule.

Genetic diversity helps life adapt to climate change

The researchers suggest that revealing a genetic basis for Bergmann's rule helps us to understand how evolution, natural selection and climate have interacted throughout a species' history.

"Our results highlight the potential role habitat conservation plays in enabling the continued exchange of genes between populations -- which is important in the face of ongoing change," said Carbeck.

Dr. Jen Walsh, a study co-author and research associate at the Cornell Lab of Ornithology, added: "From a genomic perspective, identifying a small number of candidate genes with an apparently large impact on variation in body size is really interesting. The magnificent range of phenotypic diversity seen in song sparrows suggest they offer exciting opportunities to identify genes underlying a host of well-known and generally accepted eco-geographic rules."

Dr. Peter Arcese, a co-author and a professor in UBC's department of forest and conservation sciences, said the findings suggest a resilient future for these birds.

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Rider on the storm: Shearwater seabird catches an 11 hour ride over 1,000 miles in a typhoon

New research from Japan published in the Ecological Society of America's journal Ecology suggests that increasingly severe weather driven by climate change may push oceangoing seabirds to their limits.

In August 2019, Kozue Shiomi, a seabird biologist at Tohoku University, attached GPS bio-loggers to 14 adult streaked shearwaters (Calonectris leucomelas) from a nesting colony on Mikurajima, a small island near Tokyo, as part of a study on the species homing behavior.

In September of that same year, an exceptionally powerful storm, Typhoon Faxai, barreled into southeastern Japan, causing considerable physical damage to the mainland. But the typhoon, with windspeeds nearing 200 km/hr, also provided scientists with a rare glimpse into the capacity of seabirds to withstand extreme storm conditions -- conditions that seabirds may increasingly be faced with under future climates.

Analysis of tracking data following the passage of Typhoon Faxai revealed that, while most of the tagged shearwaters appeared to be either unaffected by or had managed to circumvent the storm, one male had not been so lucky. Over the 11-hour period during which this shearwater bird was tracked, it completed five full circular loops of 50-80 km diameter each and was transported a total distance of 1,146 km.

Under normal conditions, streaked shearwaters typically fly at speeds of 10-60 km/hr and altitudes below 100 m, and remain at sea; by contrast, tracking data indicated that the bird caught in the storm had attained speeds of 90-170 km/hr, soared to an altitude of 4700 m, and was carried over mainland Japan before the typhoon swung back into the Pacific Ocean.

Although it cannot be known for certain, it is possible that the shearwater was capable of escaping from the typhoon but instead chose to ride it out until the storm moved back over the ocean. Like most birds adapted to a life at sea, streaked shearwaters typically fly at very low altitudes, an efficient flight strategy over the open ocean that also puts them at higher risk of collisions with buildings, power lines and vehicles when over land. Moreover, they are clumsy on solid ground, and if forced to land have difficulty taking off, rendering them highly vulnerable to predation.

Pelagic birds resort to a wide range of tactics to avoid being caught within the tumult of large storms. Red-footed boobies and great frigatebirds, for instance, often take to the wing and ascend to high altitudes, allowing storms to pass below, whereas Eastern brown pelicans simply sit them out, remaining grounded until conditions improve. Still others elect to stay within the eye of the storm, where winds are calmer.

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Migratory birds can be taught to adjust to climate change

One result of climate change is that spring is arriving earlier. However, migratory birds are not keeping up with these developments and arrive too late for the peak in food availability when it is time for breeding. By getting the birds to fly a little further north, researchers in Lund, Sweden, and the Netherlands have observed that these birds can give their chicks a better start in life.

Global warming is causing problems for birds in Sweden and elsewhere. Warmer springs mean that caterpillars hatch, grow and pupate earlier compared with just a few decades ago. This has consequences for birds that cannot eat caterpillars that have entered the pupal stage. Therefore, when the food supply runs out at an ever earlier time in the spring, more and more chicks starve during the breeding season. This is a big problem for migratory birds that spend winters in Africa, as they do not know how early spring arrives in Sweden. Could the problem be solved if the migratory birds simply came home and started breeding earlier?

"It seems that our non-migratory birds are doing this to a certain extent. But, of course, they are present and can feel how early spring will come. We thought that perhaps the migratory birds could fly further north until they find a place with suitable well-developed caterpillars," says Jan-Åke Nilsson, biology researcher at Lund University in Sweden.

To test this in practice, the researchers decided to help some Pied Flycatchers along the way. The biologists caught Pied Flycatchers that had arrived prior to breeding in the Netherlands. The birds were then driven during the night to Vombs Fure, an area of pine forest outside Lund in Skåne, where they were released. The peak of caterpillar availability in Skåne is about two weeks later than in the Netherlands -- a distance of around 600 kilometres that a Pied Flycatcher could cover in just two nights.

"The birds that were given a lift from the Netherlands to Skåne synchronised very well with the food peak! As they started to breed about 10 days earlier the "Swedish" Pied Flycatchers they had a dramatically better breeding success than the Swedish ones as well as a better success than the Pied Flycatchers that remained in the Netherlands," says Jan-Åke Nilsson.

In addition, it was shown that the chicks of the Dutch Pied Flycatchers that had received migration assistance did not stop in the Netherlands when they returned after their first spring migration. Instead, they continued on to the area of pine forest outside Lund where they were born. Furthermore, they arrived earlier than the Swedish Pied Flycatchers and thereby had more well-fed chicks at Vombs Fure the year after the researchers gave the Pied Flycatchers a helping hand to find Skåne.

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Most species are rare, but not very rare

More than 100 years of observations in nature have revealed a universal pattern of species abundances: Most species are rare but not very rare, and only a few species are very common. These so-called global species abundance distributions have become fully unveiled for some well-monitored species groups, such as birds. For other species groups, such as insects, however, the veil remains partially unlifted. These are the findings of an international team of researchers led by the German Centre for Integrative Biodiversity Research (iDiv), the Martin Luther University Halle-Wittenberg (MLU) and the University of Florida (UF), published in the journal Nature Ecology and Evolution. The study demonstrates how important biodiversity monitoring is for detecting species abundances on planet Earth and for understanding how they change.

"Who can explain why one species ranges widely and is very numerous, and why another allied species has a narrow range and is rare?" This question was asked by Charles Darwin in his ground-breaking book "The Origin of Species," published over 150 years ago. A related challenge has been to understand how many species are common (numerous) and how many are rare, the so-called global species abundance distribution (gSAD).

Two main gSAD models have been proposed in the last century: R. A. Fisher, a statistician and biologist, proposed that most species are very rare and that the number of species declines for more common species (so-called log-series model). On the other hand, F. W. Preston, an engineer and ecologist, argued that only few species are actually very rare and that most species have some intermediate level of commonness (so-called log-normal model). However, until now and despite decades of research, scientists did not know which model describes the planet's true gSAD.

Solving this problem calls for vast amounts of data. The study authors used data from the Global Biodiversity Information Facility (GBIF) and downloaded data representing over 1 billion species observations in nature from 1900 to 2019.

"The GBIF database is an amazing resource for all sorts of biodiversity related research, particularly because it brings together both data collected from professional and citizen scientists all over the world," says first author Dr Corey Callaghan. He began the study while working at iDiv and MLU and is now working at the UF.

Callaghan and his fellow researchers divided the downloaded data into 39 species groups, for instance, birds, insects, or mammals. For each, they compiled the respective global species abundance distribution (gSAD).

The researchers detected a potentially universal pattern, which emerges once the species abundance distribution is fully unveiled: Most species are rare but not very rare, and only a few species are very common, as predicted in the log-normal model. However, the researchers also found that the veil has been fully lifted only for a few species groups like cycads and birds. For all other species groups, the data are yet insufficient.

"If you don't have enough data, it looks as though most species are very rare," says senior author Prof Henrique Pereira, research group head at iDiv and the MLU. "But by adding more and more observations, the picture changes. You start seeing that there are, in fact, more rare species than very rare species. You can see this shift for cycads and birds when comparing the species observations from back in 1900, when less data was available, with the more comprehensive species observations we have today. It is fascinating: we can clearly see the phenomenon of unveiling the full species abundance distribution, as predicted by Preston several decades ago, but only now demonstrated at the scale of the entire planet."

"Even though we have been recording observations for decades, we have only lifted the veil for a few species groups," says Callaghan. "We still have a long way to go. But GBIF and the sharing of data really represents the future of biodiversity research and monitoring, to me."

The new study's findings enable scientists to assess how far the gSADs have been unveiled for different species groups. This allows for answering another long-standing research question: How many species are out there? This study finds that while for some groups like birds, nearly all species have been identified, this is not the case for other taxa such as insects and cephalopods.

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Human-made materials in nests can bring both risks and benefit for birds

We all discard a huge amount of plastic and other human-made materials into the environment, and these are often picked up by birds. New research has shown that 176 bird species around the world are now known to include a wide range of anthropogenic materials in their nests. All over the world, birds are using our left-over or discarded materials. Seabirds in Australia incorporate fishing nets into their nests, ospreys in North America include baler twine, birds living in cities in South America add cigarette butts, and common blackbirds in Europe pick up plastic bags to add to their nests.

This material found in birds' nests can be beneficial say researchers. For example, cigarette butts retain nicotine and other compounds that repel ectoparasites that attach themselves to nestling bird's skin and suck blood from them. Meanwhile, there are suggestions that harder human-made materials may help to provide structural support for birds' nests, while plastic films could help provide insulation and keep offspring warm. Despite such potential benefits, it is important to remember that such anthropogenic material can also be harmful to birds.

This research was published in a special issue of the Philosophical Transactions of the Royal Society B on "The evolutionary ecology of nests: a cross-taxon approach." The special issue was jointly organised by Mark Mainwaring, a Lecturer in Global Change Biology in the School of Natural Sciences at Bangor University.

Mark Mainwaring said, "The special issue highlights that the nests of a wide range of taxa -- from birds to mammals to fish to reptiles -- allow them to adapt to human-induced pressures. Those pressures range from the inclusion of anthropogenic materials into their nests through to providing parents and offspring with a place to protect themselves from increasingly hot temperatures in a changing climate."

Anthropogenic materials sometimes harm birds. Parents and offspring sometimes become fatally entangled in baler twine. Meanwhile, offspring sometimes ingest anthropogenic material after mistaking it for natural prey items. Finally, the inclusion of colourful anthropogenic materials into nests attracts predators to those nests who then prey upon the eggs or nestlings. This means that we need to reduce the amount of plastic and other anthropogenic material that we discard.

The lead author of the study, Zuzanna Jagiełło who is based at the Poznań University of Life Sciences in Poland, added, "A wide variety of bird species included anthropogenic materials into their nests. This is worrying because it is becoming increasingly apparent that such materials can harm nestlings and even adult birds."

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Fossils reveal how ancient birds molted their feathers -- which could help explain why ancestors of modern birds survived when all the other dinosaurs died

Every bird you've ever seen -- every robin, every pigeon, every penguin at the zoo -- is a living dinosaur. Birds are the only group of dinosaurs that survived the asteroid-induced mass extinction 66 million years ago. But not all the birds alive at the time made it. Why the ancestors of modern birds lived while so many of their relatives died has been a mystery that paleontologists have been trying to solve for decades. Two new studies point to one possible factor: the differences between how modern birds and their ancient cousins molt their feathers.

Feathers are one of the key traits that all birds share. They're made of a protein called keratin, the same material as our fingernails and hair, and birds rely on them to fly, swim, camouflage, attract mates, stay warm, and protect against the sun's rays. But feathers are complex structures that can't be repaired, so as a means of keeping them in good shape, birds shed their feathers and grow replacements in a process called molting. Baby birds molt in order to lose their baby feathers and grow adult ones; mature birds continue to molt about once a year.

"Molt is something that I don't think a lot of people think about, but it is fundamentally such an important process to birds, because feathers are involved in so many different functions," says Jingmai O'Connor, associate curator of fossil reptiles at Chicago's Field Museum. "We want to know, how did this process evolve? How did it differ across groups of birds? And how has that shaped bird evolution, shaped the survivability of all these different clades?" Two of O'Connor's recent papers examine the molting process in prehistoric birds.

A paper in the journal Cretaceous Research published in May 2023 detailed the discovery of a cluster of feathers preserved in amber from a baby bird that lived 99 million years ago.

Today, baby birds are on a spectrum in terms of how developed they are when they're born and how much help they need from their parents. Altricial birds hatch naked and helpless; their lack of feathers means that their parents can more efficiently transmit body heat directly to the babies' skin. Precocial species, on the other hand, are born with feathers and are fairly self-sufficient.

All baby birds go through successive molts -- periods when they lose the feathers they have and grow in a new set of feathers, before eventually reaching their adult plumage. Molting takes a lot of energy, and losing a lot of feathers at once can make it hard for a bird to keep itself warm. As a result, precocial chicks tend to molt slowly, so that they keep a steady supply of feathers, while altricial chicks that can rely on their parents for food and warmth undergo a "simultaneous molt," losing all their feathers at roughly the same time.

The amber-preserved feathers in this study are the first definitive fossil evidence of juvenile molting, and they reveal a baby bird whose life history doesn't match any birds alive today. "This specimen shows a totally bizarre combination of precocial and altricial characteristics," says O'Connor, who was the first author of the paper alongside senior author Shundong Bi of the Indiana University of Pennsylvania. "All the body feathers are basically at the exact same stage in development, so this means that all the feathers started growing simultaneously, or near simultaneously." However, this bird was almost certainly part of a now-extinct group called the Enantiornithines, which O'Connor's previous work has shown were highly precocial.

O'Connor hypothesizes that the pressures of being a precocial baby bird that had to keep itself warm, while undergoing a rapid molt, might have been a factor in the ultimate doom of the Enantiornithines. "Enantiornithines were the most diverse group of birds in the Cretaceous, but they went extinct along with all the other non-avian dinosaurs," says O'Connor. "When the asteroid hit, global temperatures would have plummeted and resources would have become scarce, so not only would these birds have even higher energy demands to stay warm, but they didn't have the resources to meet them."

Meanwhile, an additional study published July 3 in Communications Biology by O'Connor and Field Museum postdoctoral researcher Yosef Kiat examines molting patterns in modern birds to better understand how the process first evolved.

In modern adult birds, molting usually happens once a year in a sequential process, in which they replace just a few of their feathers at a time over the course of a few weeks. That way, they're still able to fly throughout the molting process. Simultaneous molts in adult birds, in which all the flight feathers fall out at the same time and regrow within a couple weeks, are rarer and tend to show up in aquatic birds like ducks that don't absolutely need to fly in order to find food and avoid predators.

It's very rare to find evidence of molting in fossil birds and other feathered dinosaurs, and O'Connor and Kiat wanted to know why. "We had this hypothesis that birds with simultaneous molts, which occur in a shorter duration of time, will be less represented in the fossil record," says O'Connor -- less time spent molting means fewer opportunities to die during your molt and become a fossil showing signs of molting. To test their hypothesis, the researchers delved into the Field Museum's collection of modern birds.

"We tested more than 600 skins of modern birds stored in the ornithology collection of the Field Museum to look for evidence of active molting," says Kiat, the first author of the study. "Among the sequentially molting birds, we found dozens of specimens in an active molt, but among the simultaneous molters, we found hardly any."

While these are modern birds, not fossils, they provide a useful proxy. "In paleontology, we have to get creative, since we don't have complete data sets. Here, we used statistical analysis of a random sample to infer what the absence of something is actually telling us," says O'Connor. In this case, the absence of molting fossil birds, despite active molting being so prevalent in the sample of modern bird specimens, suggests that fossil birds simply weren't molting as often as most modern birds. They may have undergone a simultaneous molt, or they may not have molted on a yearly basis the way most birds today do.

Both the amber specimen and the study of molting in modern birds point to a common theme: prehistoric birds and feathered dinosaurs, especially ones from groups that didn't survive the mass extinction, molted differently from today's birds.

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Which came first: The reptile or the egg?

The earliest reptiles, birds and mammals may have borne live young, researchers from Nanjing University and University of Bristol have revealed.

Until now, the hard-shelled egg was thought to be the key to the success of the amniotes -- a group of vertebrates that undergo embryonic or fetal development within an amnion, a protective membrane inside the egg.

However, a fresh study of 51 fossil species and 29 living species which could be categorised as oviparous (laying hard or soft-shelled eggs) or viviparous (giving birth to live young) suggests otherwise.

The findings, published today in Nature Ecology & Evolution, show that all the great evolutionary branches of Amniota, namely Mammalia, Lepidosauria (lizards and relatives), and Archosauria (dinosaurs, crocodilians, birds) reveal viviparity and extended embryo retention in their ancestors.

Extended embryo retention (EER) is when the young are retained by the mother for a varying amount of time, likely depending on when conditions are best for survival.

While the hard-shelled egg has often been seen as one of the greatest innovations in evolution, this research implies it was EER that gave this particular group of animals the ultimate protection.

Professor Michael Benton from the Bristol's School of Earth Sciences explained: "Before the amniotes, the first tetrapods to evolve limbs from fishy fins were broadly amphibious in habits. They had to live in or near water to feed and breed, as in modern amphibians such as frogs and salamanders.

"When the amniotes came on the scene 320 million years ago, they were able to break away from the water by evolving waterproof skin and other ways to control water loss. But the amniotic egg was the key. It was said to be a 'private pond' in which the developing reptile was protected from drying out in the warm climates and enabled the Amniota to move away from the waterside and dominate terrestrial ecosystems."

Project Leader Professor Baoyu Jiang added: "This standard view has been challenged. Biologists had noticed many lizards and snakes display flexible reproductive strategy across oviparity and viviparity.

"Sometimes, closely related species show both behaviours, and it turns out that live-bearing lizards can flip back to laying eggs much more easily than had been assumed."

"Also, when we look at fossils, we find that many of them were live-bearers, including the Mesozoic marine reptiles like ichthyosaurs and plesiosaurs," said Dr Armin Elsler. "Other fossils, including a choristodere from the Cretaceous of China, described here, show the to-and-fro between oviparity and viviparity happened in other groups, not just in lizards."

Dr Joseph Keating explained: "EER is widespread among vertebrates today, where the developing young are retained by the mother for a lesser or greater span of time.

"EER is common and variable in lizards and snakes today. Their young can be released, either inside an egg or as little wrigglers, at different developmental stages, and there appears to be ecological advantages of EER, perhaps allowing the mothers to release their young when temperatures are warm enough and food supplies are rich."

Professor Benton concluded: "Our work, and that of many others in recent years, has consigned the classic 'reptile egg' model of the textbooks to the wastebasket.

"The first amniotes had evolved extended embryo retention rather than a hard-shelled egg to protect the developing embryo for a lesser or greater amount of time inside the mother, so birth could be delayed until environments become favourable.

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For birds, blending in may result in more diversity

The saying "Birds of a feather flock together" is being given new meaning by a study published in the Philosophical Transactions of the Royal Society b. Flocking birds often travel in groups made up of a single species, in which individuals are nearly indistinguishable from one another, as noted by the proverbial adage. But something strange happens in flocks of two or more species from Southeast Asia. Even when flock species are distantly related, they still seem to converge on the same appearance, as if trying to fit in.

"They all share haphazard traits, like crests or yellow bellies, which makes them almost identical. You can't really tell them apart without looking at their markings," said study co-author Scott Robinson, Ordway eminent scholar at the Florida Museum of Natural History.

According to Robinson, this similarity in plumage is likely a type of mimicry, which by itself isn't uncommon in birds. Alfred Russel Wallace, the co-discoverer of natural selection, was the first to suggest that some bird species engage in mimicry when noting the similarities between orioles and friarbirds in Australia. Birds can mimic one another to reduce aggression from a dominant species; to resemble a more formidable adversary to predators; and, in at least one case, to make themselves appear toxic.

But resemblance in multispecies flocks is something different, said lead author Rebecca Kimball, professor of biology at the University of Florida.

"In mimicry, you often want to look like something because there's an advantage to being that other thing. You want species to think you're toxic or low-profitable prey," she said. "In flocking birds, one idea is that this has more to do with a predator's ability to isolate a target. When there are a bunch of birds moving around, it may be easier for predators to identify an individual that has a distinct color pattern."

This idea that unrelated birds find safety in collective obscurity was first proposed in the 1960s for flocks along the Andes Mountains. But follow-up studies failed to show conclusive evidence of mimicry in Andean multispecies flocks, and the theory was largely abandoned.

"The idea sat fallow for a long time," Robinson said. But in 2010, Robinson began working with a Chinese colleague in Yunnan province and observed what appeared to be the same phenomenon that had been described decades earlier.

Robinson and his colleagues spent the next several years documenting similarities in China's multispecies flocks, uncovering the same pattern again and again. While some of the similarities between species are subtle, the authors points to several visually conspicuous examples.

In western Asia, Himalayan cutias (Cutia nipalensis) look like they're dressed in mismatched layers, with a mask of black feathers, chestnut wings, and white chests with zebra stripes. This pattern might seem impervious to emulation, yet the rufous-backed sibias (Leioptila annectens) they flock with do a remarkably good impression. Both species have similar behavior, foraging patterns and markings, with the exception of stripes, which the sibias lack.

Some birds also seem capable of mimicking more than one species as they mature. Juvenile white-hooded babblers (Gampsorhynchus rufulus) have rusty head feathers, brown wings and creamy underbellies, similar to the parrotbills they flock with. Adults look like an entirely different species, with white heads and dark brown wings that resemble white-crested laughingthrushes (Garrulax leucolophus), all of which are part of the same flock.

Somewhat counterintuitively, this conformity within multispecies flocks may be contributing to diversity in the region. Not only can birds mimic more than one species at different stages of development, but their appearance can also vary across their range. In eastern China, coal tits tag along with birds with prominent crest feathers, which they mimic. In the Himalayas and Hengduan Mountains farther west, the same species lacks a crest and flocks with other crestless birds.

If these differences persist long enough, Robinson said, it might ultimately result in one species becoming two. "The possible role this type of mimicry plays in speciation is the most interesting idea from our point of view. Many of these birds have huge ranges, and there may be a lot of differentiation in these traits involved in flocking within a species."

There seem to be two main ingredients required to create this type of mimicry in flocks, both of which might help explain why this pattern appears to be so prominent in China but absent elsewhere.

First, Robinson said, a flock must be composed of just a few species, with some more common than others. "When you have a flock with a really dominant, abundant species, there's a model worth mimicking. If other birds look like that model, they get the same protection, they get access to the same resources, and they get to travel with a compatible group."

In other parts of the world, many flocks have more of an open-door policy, weakening the selective forces that contribute to mimicry. Mating pairs of multiple species join together in patchwork groups, often relying on the warning calls of sentries to avoid predators rather than their ability to fade into the background.

The second ingredient is the winnowing fan of predation. For small to medium flocking birds, the biggest source of danger comes from above, in the form of raptors, and the skies above Southeast Asia are especially fraught. The region encompasses only 3% of Earth's land area, yet it harbors almost 30% of all raptor species. This puts an enormous amount of pressure on flocks, Robinson said, which may promote mimicry.

To determine whether similarity among flocking species is the result of mimicry, the authors say they'll need to conduct widescale genetic analyses to rule out other potential causes.

Read more at Science Daily

The surprising science behind long-distance bird migration

A team of scientists led by researchers at the University of Massachusetts Amherst has recently made a surprising discovery, with the help of a wind tunnel and a flock of birds. Songbirds, many of which make twice-yearly, non-stop flights of more than 1,000 miles to get from breeding range to wintering range, fuel themselves by burning lots of fat and a surprising amount of the protein making up lean body mass, including muscle, early in the flight. This flips the conventional wisdom on its head, which had assumed that migrating birds only ramped up protein consumption at the very end of their journeys, because they would need to use every ounce of muscle for wing-flapping, not fuel. The results appeared recently in the Proceedings of the National Academy of Sciences.

"Birds are amazing animals," says Cory Elowe, the paper's lead author and a postdoctoral researcher in biology at UMass Amherst, where he received his Ph.D. "They are extreme endurance athletes; a bird that weighs half an ounce can fly, non-stop, flapping for 100 hours at a time, from Canada to South America. How is this possible? How do they fuel their flight?"

For a very long time, biologists assumed that birds fueled such feats of endurance by burning fat reserves. And indeed, fat is an important part of migratory birds' secret mix. "The birds in our tests burned fat at a consistent rate throughout their flights," says Elowe. "But we also found that they burn protein at an extremely high rate very early in their flights, and that the rate at which they burn protein tapers off as the duration of the flight increases."

"This is a new insight," says Alexander Gerson, associate professor of biology at UMass Amherst and the paper's senior author. "No one has been able to measure protein burn to this extent in birds before."

"We knew that birds burned protein, but not at this rate, and not so early in their flights," continues Gerson. "What's more, these small songbirds can burn 20% of their muscle mass and then build it all back in a matter of days."

To make this breakthrough, Elowe had help from the bird banding operators at Long Point Bird Observatory, in Ontario, along the northern shore of Lake Erie. Every fall, millions of birds gather near the observatory on their journey to their wintering grounds -- including the blackpoll warbler, a small songbird that travels thousands of miles during its migration. After capturing 20 blackpolls and 44 yellow-rumped warblers -- a shorter distance migrant -- using mist nets, Elowe and his colleagues then transported the birds to the Advanced Facility for Avian Research at Western University, which has a specialized wind tunnel built specifically for observing birds in flight.

Elowe measured the birds' fat and lean body mass pre-flight, then, when the sun set, let the birds free in the wind tunnel. Because the birds naturally migrate at night, Elowe and his colleagues would then stay awake -- at one point, for 28 hours -- watching for when a bird would decide to rest. At that point, the researchers would collect the bird and again measure its fat and lean body mass content, comparing them with the pre-flight measurements.

"One of the biggest surprises was that every bird still had plenty of fat left when it chose to end its flight," says Elowe. "But their muscles were emaciated. Protein, not fat, seems to be a limiting factor in determining how far birds can fly."

The researchers still don't quite know why the birds are burning such vast stores of protein so early in their journeys, but the possible answers open up a wide range of future research avenues.

"How exactly is it possible to burn up your muscles and internal organs, and then rebuild them as quickly as these birds do," wonders Gerson. "What insights into the evolution of metabolism might these birds yield?"

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Most of world's salt marshes likely to be underwater by 2100, study concludes

Cape Cod's salt marshes are as iconic as they are important. These beautiful, low-lying wetlands are some of the most biologically productive ecosystems on Earth. They play an outsized role in nitrogen cycling, act as carbon sinks, protect coastal development from storm surge, and provide critical habitats and nurseries for many fish, shellfish, and coastal birds.

And, according to new research from the Marine Biological Laboratory (MBL), more than 90 percent of the world's salt marshes are likely to be underwater by the end of the century.

The findings come from a 50-year study in Great Sippewissett Marsh in Falmouth, Massachusetts. Since 1971, scientists from the MBL Ecosystems Center have mapped vegetative cover in experimental plots in this marsh to examine whether increased nitrogen in the environment would impact species of marsh grass. Due to the study's length, they also were able to detect the effects of climate change on the ecosystem, especially those driven by accelerating sea level rise.

The researchers found that increased nitrogen favored higher levels of vegetation and accretion of the marsh surface, but that no matter what the concentration of nitrogen they applied to the marsh, these ecosystems won't be able to outpace submergence from global sea level rise.

"Places like Great Sippewissett Marsh will likely become shallow inlets by the turn of the century," says MBL Distinguished Scientist Ivan Valiela, lead author of the study. "Even under conservative sea level estimates…more than 90% of the salt marshes of the world will likely be submerged and disappear or be diminished by the end of the century."

"This is not a prediction from isolated scientists worried about little details. Major changes are going to be taking place on the surface of the Earth that will change the nature of coastal environments," says Valiela.

An Ecosystem Engineer

Salt marshes are gently sloping ecosystems and their plants have very narrow preferences for the elevations in which they can grow. Different species grow in the upper elevations (high marsh) versus the low elevation closer to the ocean (low marsh) and have different responses to changes in nitrogen supply. When change happens slowly enough, the grasses can migrate to their preferred elevation.

In the low marsh, cordgrass (Spartina alterniflora) prospered as scientists increased the nitrogen supply. Among high marsh species, the abundance of marsh hay (Spartina patens) in the experimental plots decreased with sea level rise. Saltgrass (Distichlis spicata) increased with nitrogen supply and also acted as what the researchers called an "ecosystem engineer" -- increasing the rate at which marsh elevation rose. Accretion of biomass left behind by the decomposing saltgrass compensated for the increased submergence resulting from rising sea level in these areas.

"Saltgrass disappeared after a few decades, but it left a legacy behind," says MBL Research Scientist Javier Lloret, adding that it was "extremely cool to see that interaction in the dataset."

Regardless of how much nitrogen was added to the environment, the research showed that at the current and future forecasted sea level rise, low marsh species will completely replace high marsh species. As sea levels continue to rise, even these species will be submerged.

"At some point, if sea level continues to increase at the rates that we anticipate, there will even be no more room for the low marsh plants. They're just going to be too submerged to survive." says Valiela.

The only alternative would be for salt marshes to migrate landward.

A Coastal Squeeze

Marshes around the world face what Lloret calls a "coastal squeeze," where sea level rise pushes from one direction and human development pushes from the other. A seawall that may protect a home from flooding will prevent the migration of a marsh naturally moving to higher ground.

"These barriers, whether they be geographic like a hill or a cliff, or people building along the edges of the ecosystem, constrain the potential for landward marsh migration," says MBL Research Assistant Kelsey Chenoweth. "On top of that, sea level rise is accelerating and marshes are having a hard time keeping up."

In a sea level rise scenario like the one we're facing, "the only solution for the plants will be to colonize new areas, to go uphill," says Lloret. "But that migration may just be impossible in some places."

"Sea level rise is the most important threat to salt marshes. We really need to figure out what's going to happen to these ecosystems and learn how to prevent some of the losses from happening or try to adapt to them, so marshes can continue to play these important roles for nature as well as humans," says Lloret.

Half a Century of Science

In 1971, the scientists at the MBL Ecosystems Center had no idea they would be using their data to study global sea level rise.

"This was an experiment that started looking at one ecological control (nitrogen), and then because of the longevity of the project, we were able to add new knowledge about this major accelerating agent of global change -- global sea level rise," says Valiela.

That's the benefit of long-term datasets like the one at Great Sippewissett Marsh.

"You're setting a baseline to the problems that haven't even happened yet," says Chenoweth.

When measuring ecological processes like climate change and eutrophication, the data can ebb and flow over the course of years as the ecosystem responds to external stimuli. The changes operate on a much longer time scale than changes on other biological systems.

"To study a tree, you look at changes through seasons and you should be able to see its whole cycle. For a leaf, you look at patterns between day and night. In single cells, you look at processes that take place at the timescale of minutes or seconds … but for an entire ecosystem, we're talking many years or decades," says Lloret. "You need to be thinking at the scale of decades or even centuries in order to be able to see substantial changes."

Read more at Science Daily