Adak Island lies between 51”35’ and 52”Ol’ N. and 176”25’ and 176”59’ W, in the Andreanof Group, Aleutian Islands. Although Taber (1946) provides an annotated list of birds he observed at Adak in winter, year-round observations have not been previously published. Since Adak lies near the middle of the axis formed by the Alaska Peninsula and the Aleutian and Commander islands (fig. l), which links North America and Asia, its avifauna is composed of species with varied geographic origins. Closely paralleling the findings of Emison et al. (1971), who discuss the geographic origins of 100 species of birds known from Amchitka Island, 65% (81 species) of the birds recorded at Adak have contemporary breeding distributions in both North America and Asia (vs. 68% at Amchitka) ; 19% (24 spp.) have affinities only to Asia (vs. 15%); 12% (15 spp.) have affinities only to North America (vs. 13%); and 3% (4 spp.) breed only on midand south Pacific islands (vs. 4%). Of the 124 species included in the following annotated list, two, Anas poecilorhyncha zonorhyncha and Cuculus canorus canorus, are new to North America. Seventeen additional forms are represented by few North American records, and well over half of the species listed have not been previously recorded on Adak.