Newly discovered bone fragments from Alaska suggest birds have been breeding and nesting in the Arctic for at least 73 million years.

鈥淲hich is kind of crazy, because it鈥檚 not easy to live in the Arctic and have newborn babies up there,鈥� says study author at Princeton University.

Today, about 250 bird species have adapted to thrive at Earth鈥檚 poles. Some migrate great distances and only spend the summers there, with 24 hours of light each day. Others stay over winter too, enduring frigid temperatures and perpetual darkness for weeks on end. But very little was known about how and when these birds first got to the highest latitudes of Earth.

Wilson and her colleagues searched for traces of ancient birds in a sequence of rocks known as the Prince Creek Formation in northern Alaska, which were formed on a coastal floodplain about 73 million years ago. At that time, what is now northern Alaska was about 1000 to 1600 kilometres nearer the North Pole than it is today.

The team recovered chunks of ancient soil from some thin rock layers in the formation. This was during the winter, when temperatures were -30掳C (-22掳F) and home was a tent. 鈥淚t鈥檚 definitely the most intense field work I鈥檝e ever done,鈥� says Wilson.

Back in the laboratory, they 鈥渟pent hours staring鈥� through a microscope 鈥渁t grains of sediment that are smaller than two millimetres鈥�, says Wilson, hunting through them carefully for tiny fragments of fossil bone.

They uncovered more than 50 ancient bird fossil fragments, many of which came from chicks or even embryonic birds. The fossilised bones of such young birds have a sponge-like texture because they represent a stage when bones are growing rapidly.

While birds probably began nesting in the Arctic even earlier than 73 million years ago, the fossils are the oldest traces of this behaviour found to date. They push back the record of this in birds by 30 million years.

Still, the fossils are very fragmented. They also don鈥檛 show whether the birds lived there year-round or just during the warmer summers.

鈥淭he Arctic as we know it, especially those food webs that eke out an existence in the cold and dark, could not exist without the many birds that call the high latitudes home,鈥� says at the University of Edinburgh, UK, who wasn鈥檛 involved in the study. 鈥淭hese fossils show that birds were already integral parts of these high-latitude communities many tens of millions of years ago.鈥�

Wilson鈥檚 team could identify three main groups of birds among the fossil fragments: extinct toothed birds similar to loons, extinct toothed birds similar to gulls, and some species that may belong to the same group as all modern birds.

The samples, though, didn鈥檛 have any bones from a group of more archaic birds known as the enantiornithines 鈥� or 鈥�opposite birds鈥� 鈥� which dominate the fossil records from that time all over the rest of the world. at the Senckenberg Research Institute in Germany, who also wasn鈥檛 involved in the study, thinks this is a 鈥渟ignificant鈥� finding that could suggest that the ancestors of more advanced birds could cope with harsh Arctic conditions because of some unique evolutionary traits that the ancestral birds lacked.

The ecosystem that gave rise to the Prince Creek Formation existed at a time when the large non-bird dinosaurs still ruled the world, and fossils suggest the ancient birds shared these Arctic ecosystems with species of tyrannosaur and horned ceratopsians. There is even evidence that some of those dinosaurs nested in the Arctic as well.

These images from the Earth Photo 2025 competition shortlist tell revealing, inspiring and unexpected stories about the climate and life on our planet.

Pictured top, photographer Ami Vitale鈥檚 image Pandamonium shows a giant panda keeper checking the health of a panda cub in the Wolong National Nature Reserve in Sichuan province, China. The keeper鈥檚 outfit is part of an effort to reduce the impact of human contact on the bears. Next, below, is Sue Flood鈥檚 Crabeater Seals, shot on an ice floe in the Southern Ocean, off the Antarctic Peninsula. For Flood, such photos can bring the region鈥檚 wonder to those who may never visit.

Paradise to Ashes, La Palma by Jonathan Browning pictured below, shows the aftermath of the 2021 Cumbre Vieja volcanic eruption on this island in the Canaries, Spain. A woman has remade her garden, removing lava that destroyed mature palms and replacing them with new trees.

The final image below is Vincenzo Montefinese鈥檚 Lost Oases, shot in Tinzouline, Draa valley, Morocco. Here, a man adjusts a solar panel that powers a water pump that irrigates nearby palm groves. Climate change and water use have shrunk the valley鈥檚 oases by two-thirds over the past century. Today, farmers must dig more wells, often illegally, to access groundwater.

The photos and videos on the shortlist were chosen by a panel including 快猫短视频 picture editor Tim Boddy and head of editorial video, David Stock. The winners will be revealed on 16 June. The Earth Photo 2025 exhibition is at London鈥檚 Royal Geographical Society from 17 June to 20 August before it tours the UK.