Scientists Find the First Evidence of Birds Nesting in the Arctic Alongside Dinosaurs
The researchers analyzed rare fossils of hatchling birds found in northern Alaska, which offered the earliest evidence of the creatures reproducing in a polar region
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Early birds were nesting in the cold landscape of the Arctic during the age of the dinosaurs, according to a new study published in Science last week.
Researchers analyzed more than 50 avian fossils unearthed in northern Alaska—including bones from embryos and hatchlings—and found evidence that birds have been nesting at Arctic latitudes since at least 73 million years ago, during the Cretaceous period.
“Which is kind of crazy, because it’s not easy to live in the Arctic and have newborn babies up there,” says lead author Lauren Wilson, a vertebrate paleontologist at Princeton University, to Sofia Quaglia at New Scientist.
More than 200 modern bird species nest in the Arctic, braving the harsh conditions each year. But these birds will migrate out of the area over the winter or have adapted to the freezing temperatures. The study shows this adaptation happened much earlier than thought—the previous oldest known evidence of birds nesting near the poles was a collection of immature penguin fossils from Antarctica, dating to between 40.5 million and 46.5 million years ago.
Scientists didn’t think early birds were capable of breeding in polar regions. “The common conception is they’re too primitive to be exhibiting this advanced behavior,” Wilson tells Jesse Steinmetz at Live Science. “So you’re either dealing with [Arctic winters] as an itty-bitty, freshly hatched bird, or you’re 3 months old and having to fly about 2,000 kilometers [1,240 miles] to get to a point where it makes sense to even migrate. I don’t think we would expect either of those things from these birds that don’t belong to that modern lineage of birds.”
To find the fossils, Wilson and her colleagues searched near the Prince Creek Formation, an area of Alaska known for its dinosaur fossils that would have been at least 600 miles closer to the North Pole during the Cretaceous than it is today. They recovered pieces of screened sediment and examined them under a microscope at their lab, where they spent hours carefully staring at the grains to pick out bones, she tells New Scientist.
“These new fossils fill a major gap in our understanding of bird evolution,” says Patrick Druckenmiller, director of the University of Alaska Museum of the North and a study co-author, to Nicola Davis at the Guardian. Not only that, but the work places Alaska on the map for further bird fossil collections. “It wasn’t on anyone’s radar,” adds Druckenmiller in a statement.
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The fact that these fossils still exist is impressive, say the researchers. That’s because of how delicate bird bones are, especially those of the baby birds examined by the team. Fossil bones from hatchlings have a spongy and porous texture, which makes them more fragile compared to adults’ bones.
“Finding bird bones from the Cretaceous is already a very rare thing,” Wilson says in the statement. “To find baby bird bones is almost unheard of. That is why these fossils are significant.”
The fossils come from three main groups; hesperornithes, which are extinct, loon-like toothed birds; ichthyornithes, which are extinct, gull-like toothed birds; and species resembling modern ducks, according to Live Science. The researchers did not find any fossils from enantiornithines, an extinct bird group that was dominant during the Cretaceous.
Gerald Mayr, an ornithologist at the Senckenberg Research Institute in Germany who was not involved in the research, tells New Scientist that that is a significant finding, because it could mean that the ancestors of today’s more advanced birds could handle tough Arctic conditions, thanks to traits that the enantiornithines did not have.
While the world was warmer overall during the Late Cretaceous, the Arctic was still freezing. And the birds breeding there had another problem to face: dinosaurs. Some of these giant beasts “would have happily taken advantage of a bunch of these little cute little chicks for dinner,” says Druckenmiller to Live Science.
Overall, the tiny fossils tell a huge story, says Steve Brusatte, a paleontologist at the University of Edinburgh who was not involved in the study, to the Guardian.
“These fossils show that birds were already integral parts of these high-latitude communities many tens of millions of years ago, and thus that these communities are a long-term norm of Earth history, not a recent ecological innovation of modern times,” he says.
