For two centuries, invasive rats on the island have ravaged populations of ground-nesting seabirds. In September, Island Conservation, the Nature Conservancy, and the U.S. Fish and Wildlife Service dropped rat poison from helicopters after an environmental assessment concluded birds were unlikely to be harmed because the rodents would perish in their burrows.

A recent census found puffins and other seabirds were returning to nest on the island in the absence of rats. But wildlife workers also discovered corpses from 43 bald eagles, 213 glaucous-winged gulls, and several other species. The scientists believe gulls may have consumed the poison cakes and were then preyed upon by eagles.