TROMSØ, Norway Construction cranes tower stork-like over the skyline of this burgeoning burg 200-plus miles above the Arctic Circle. Spurred by a recent flood of adventurers chasing the northern lights and sightseers wanting a glimpse of the glaciers before they’re gone, this tourism hub on Norway’s north coast has been building hotels geared for an anticipated 2.3 million visitors a year.

While the human tourist boom is on hold for now, some visitors are still flocking in and looking for suitable places to stay. These guests are black-legged kittiwakes—the most seafaring member of the gull family, and one that is facing an uncertain future.

Usually, kittiwakes nest in cliffs over the ocean and seldom venture inland. But in the past few years from