Arctic Avialans: 73-Million-Year-Old Perinatal Fossils Prove Birds Nested at Polar Laтιтudes Alongside Dinosaurs

In a cover-featured Science paper published May 29, 2025, Lauren Wilson and colleagues have delivered the oldest direct evidence that birds nested in the Arctic—73 million years ago, during the Late Cretaceous, at paleolaтιтudes of 80–85°N in what is now northern Alaska.

Excavated from the Prince Creek Formation along the Colville River, the remarkable ᴀssemblage includes more than 50 perinatal fossils—tiny bones and teeth from embryos and hatchlings—representing multiple avialan lineages. These include diving birds akin to hesperornithines, gull-like forms, and early relatives of ducks and geese. The fossils were recovered through a decade-long microfossil screen-washing program of channel-lag deposits, yielding one of the most complete Late Cretaceous avifaunas known.

The Prince Creek environment featured continuous summer daylight for nearly six months, seasonal flooding, and a mosaic of conifer forests and wetlands where non-avian dinosaurs, mammals, and fish also thrived. The presence of abundant hatchling remains in the same beds as adult birds confirms active nesting rather than post-mortem transport.

“This pushes the record of polar bird reproduction back at least 25–30 million years,” Wilson noted. The discovery demonstrates that seasonal nesting in extreme laтιтudes originated in Mesozoic avialans—long before the post-Cretaceous radiation of modern birds—and that this behavior was already widespread among early euornithines.

The Alaskan fossils prove that birds were not merely surviving at the poles but successfully reproducing there alongside dinosaurs, revealing sophisticated migratory and reproductive strategies that persist in today’s Arctic avifauna. After 73 million years, these tiny perinatal bones have rewritten the deep history of polar ecosystems.