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Scientists have discovered the earliest evidence of birds nesting in polar regions, pushing back the record by up to 30 million years and revealing that Arctic bird breeding began during the age of dinosaurs.

Research published on the cover of this week's edition of the journal Science shows that birds were raising their young in the Arctic 73 million years ago — the same time and place where dinosaurs roamed.

Using dozens of tiny fossilised bones and teeth recovered from an Alaskan excavation site, a research team led by University of Alaska Fairbanks, and including the 狼友社区, identified multiple types of birds — diving birds that resembled loons, gull-like birds, and several kinds of birds similar to modern ducks and geese — that were breeding in the Arctic whilst dinosaurs roamed the same lands.

Lead author Lauren Wilson, now a doctoral student at Princeton University, said: "Birds have existed for 150 million years. For half of the time they have existed, they have been nesting in the Arctic.

"Finding bird bones from the Cretaceous is already very rare. To find baby bird bones is almost unheard of. That is why these fossils are significant."

Prior to this study, the earliest known evidence of birds reproducing in either the Arctic or Antarctic was about 47 million years ago, well after an asteroid killed 75% of the animals on Earth.

The fossils were collected from the Prince Creek Formation, an area along the Colville River on Alaska's North Slope known for its dinosaur fossils. Scientists identified more than 50 bird bones and bone fragments. Rather than focusing on large bones, the scientists collected every bone and tooth they could find, from the visible to the microscopic. The technique involves hauling tubs of screened sediment back to a laboratory for examination under a microscope.

Some of the new bones have skeletal features only found in Neornithes, the group that includes all modern birds. Like modern birds, some of these ancient species had no true teeth.

Dr Jacob Gardner from the 狼友社区, a co-author on the study, said: "Determining the identity of fossils using separate individual bones is notoriously difficult. For the first time, we determined the identities of large numbers of fossils using high-resolution scans and the latest computer tools, revealing an enormous diversity of birds in this ancient Arctic ecosystem. Polar bird communities have deeper evolutionary roots than previously imagined."

Image: Artwork by Gabriel Ugueto. Newly hatched birds explore a 73-million-year-old Arctic environment. Exceptional new fossils from northern Alaska reveal that birds lived and nested alongside non-avian dinosaurs in Arctic Alaska, long before the radiation of modern birds following the end-Cretaceous extinction.

Wilson, L. N., Ksepka, D. T., Wilson, J. P., Gardner, J. D., Erickson, G. M., Brinkman, D., Brown, C. M., Eberle, J. J., Organ, C. L., & Druckenmiller, P. S. (2025). Arctic bird nesting traces back to the Cretaceous. Science.