(Modified from UAF Press Release by Marmian Grimes)

Each Spring, millions of birds gather in the Arctic to nest and raise their young. They benefit from the abundant summer food resources that are a product of the high-latitude summer light regime, with up to 6 months of continuous daylight.

But this behavior isn’t new; the same was true 73 million years ago, according to a paper led by current Department of Geosciences Ph.D. student Lauren Wilson, featured on the cover of this week’s edition of the journal Science. The paper documents the earliest-known example of birds nesting in the polar regions.

“Birds have existed for 150 million years,” said lead author Lauren Wilson, who earned her master’s degree at the University of Alaska Fairbanks (UAF). “For half of the time they have existed, they have been nesting in the Arctic.”

The paper is the result of Wilson’s master’s thesis research at UAF. Using dozens of tiny fossilized bones and teeth from several Alaskan excavation sites, she and her colleagues 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 while dinosaurs roamed the same lands.

Prior to this study, the earliest known evidence of birds reproducing in polar regions was a penguin colony from Antarctica about 47 million years ago, well after an asteroid killed 75% of the animals on Earth at the end of the Cretaceous Period 66 million years ago.

“This pushes back the record of birds breeding in the polar regions by 25 to 30 million years,” said Pat Druckenmiller, the paper’s senior author, director of the University of Alaska Museum of the North and Wilson’s advisor for her master’s degree work. 

The mere existence of the large collection of ancient bird fossils is remarkable, Wilson said, given how delicate bird bones are. That is doubly true for baby bird bones, which are porous and easily destroyed.

“Finding bird bones from the Cretaceous is already a very rare thing,” she said. “To find baby bird bones is almost unheard of. That is why these fossils are significant.”

The fossils were collected from the Prince Creek Formation, a sedimentary rock formation exposed along the modern Colville River on Alaska’s North Slope, known for its dinosaur fossils. Scientists identified more than 50 bird bones and bone fragments.

“We put Alaska on the map for fossil birds,” Druckenmiller said. “It wasn’t on anyone’s radar.”

The collection is a testament to the value of an uncommon excavation and research approach at the Prince Creek Formation. Much of vertebrate paleontology focuses on recovering large bones.’

The scientists who work in the Prince Creek Formation make sure to get every bone and tooth they can, from the visible to the microscopic, Druckenmiller said. The technique, which involves hauling tubs of screened sediment back to the lab for examination under a microscope, has yielded numerous new species and unprecedented insights into the behavior and physiology of the dinosaurs, birds, and mammals that lived in the Arctic during the Cretaceous Period.

“Every day in the lab was an adventure. Some days I would sort through the minuscule fossils picked from the sediment, hoping for more bird bones. Sure enough, some days a baby bird foot bone would show up, and the next day maybe a wing bone would appear, and on and on,” says John Wilson, currently the Collections Manager in the Department of Geosciences at Princeton University and who prepared many of the fossils for this study. “We could watch this sample expanding in real time, putting together this incredible view of bird behavior in the age of dinosaurs.”

“We are now one of the best places in the nation for bird fossils from the age of the dinosaurs,” Druckenmiller said. “In terms of information content, these little bones and teeth are fascinating and provide an incredible depth of understanding of the animals of this time.”

It remains to be seen whether the bones found on the Colville River are the earliest-known members of Neornithes, the group that includes all modern birds. Some of the new bones have skeletal features only found in this group. And, like modern birds, some of these birds had no true teeth.

“If they are part of the modern bird group, they would be the oldest such fossils ever found,” Druckenmiller said. Currently, the oldest such fossils are from about 69 million years ago. “But it would take us finding a partial or full skeleton to say for sure.”

Other collaborators on the paper include Daniel Ksepka from the Bruce Museum, Jacob Gardner from the University of Reading, Gregory Erickson from Florida State University, Donald Brinkman and Caleb Brown from the Royal Tyrrell Museum of Palaeontology and the University of Alberta (Brown is also affiliated with the University of Manitoba), Jaelyn Eberle from the University of Colorado Boulder and Chris Organ from Montana State University.

The article, Arctic bird nesting traces back to the Cretaceous, first appeared online May 29 in Science.