How Birds Began Migrating to the Arctic to Breed

Tiny fossils from northern Alaska hint that birds began migrating to the Arctic to breed as far back as 73 million years ago. These fossils, dating to the Late Cretaceous period, are the earliest known evidence of birds reproducing at polar latitudes. The birds likely took advantage of the Arctic's seasonal conditions, including abundant food and 24-hour daylight, to raise their young. These early migratory birds may have been the ancestors of today's Arctic-breeding species.