Populations and habitat use of marine birds in the Semidi Islands, Alaska

About one-quarter of the resident seabirds in the Gulf of Alaska breed on the Semidi Islands. In terms of biomass, the proportion is closer to one-third. The most abundant birds are Common and Thick-billed Murres, with a combined population exceeding 1 million birds. Hundreds of thousands of Horned Puffins breed in burrows on two islands. Other species numbering more than 100,000 individuals include the Northern Fulmar, Fork-tailed and Leach's Storm-Petrels, and possibly also the Black-legged Kittiwake and Tufted Puffin. Both species of storm-petrels commonly nest in side chambers of puffin burrows. Parasitic Jaegers nest in a loose colony on Chowiet Island. This behavior has not been reported elsewhere in the Gulf of Alaska. Red-faced and Pelagic Cormorants commonly change breeding colony location from year to year. The Semidi Islands are the easternmost breeding site for Least Auklets.