The rats appear to be gone from Alaska's Rat Island, more than 200 years after they scurried off a rodent-infested Japanese ship.
Helicopters dropped rat poison on the island last year in hopes of returning many bird species to the uninhabited island in the Aleutian Chain.
The U.S. Fish and Wildlife Service says two weeks of intensive monitoring shows no sign of invasive rats. It also shows that several bird species, including peregrine falcons and black oystercatchers, were nesting on the island.
Scientists did find numerous carcasses of two types of birds: glaucous-winged gulls and bald eagles. The federal agency is conducting tests to try to determine why they died.
A shipwreck in 1780 brought rats to the island located some 1,700 miles from Anchorage.