Once common in the Rocky Mountain West, trumpeter swans have been a rare sight for more than a century after hunters blasted them from the sky to cash in on their skins and plumage, then in demand for women’s hats and other accessories.

Now the bird, North America’s largest and the world’s heaviest capable of flight, is coming back strong in parts of its historic range, thanks to reintroductions and prohibitions on hunting them. Yet, in Utah, they are falling in growing numbers…