“There’s a really good reason all these birds are flying several thousand miles just to eat and raise their young and then turn around a couple months later and fly back,” said Melanie Smith, a scientist with Audubon Alaska.

The high cliffs of the Colville uplands are ideal habitat for birds of prey. The wide delta, with its fan of freshwater channels flowing into saltwater, provides a variety of plant and marine food to support globally significant populations of migrating shorebirds.

Vast Teshekpuk Lake and other lakes and ponds that dot the tundra shelter molting waterfowl.

“If you’re a goose and you can’t fly for a few weeks, you need to be out in the middle of a lake where you can’t get picked off by a fox or something,” Smith said. And Kasegaluk Lagoon, on the western part of the North Slope, has shallow, sheltered waters with plentiful food for birds stopping by during long migrations, she said.

To Fiorillo, it is fitting that the region that once was home to dinosaurs is now a haven for birds.

In the past, scientists pondered the similarities between dinosaurs and birds, with their common beaks, claws and egg-laying habits and sometimes feathers. Now they’ve concluded that the relationship is a direct line of descent.

“We now know that birds are dinosaurs,” Fiorillo said.