Two subspecies of Herring Gulls frequent the Bering Sea region. Various authorities have suggested that the two forms are sufficiently distinctive that they warrant specific status. Herring Gulls (considering both subspecies together) are uncommon from mid-summer to fall, and rare in spring. The number of individuals recorded in spring is highly year dependent. In general, the old world formLarus argentatus vagae, hereafter referred to as Vega Gull is the more likely form to be encountered on the Pribilofs. Small to moderate numbers of the American Herring Gull (Larus argentatus smithsonianus) occur annually, primarily in mid summer though fall. Vega Gulls can be identified if seen well by their generally darker mantles, red orbital rings and brown to golden-brown irises. In comparison, American Herring Gulls have paler, more silvery mantles, thin yellow or yellow-orange orbital rings and bright yellow irises. The separation of first year birds must be based on the tail pattern. Vegae Gull’s show a broad band at the tail tip, while most American Herring Gulls will show an all-dark tail. First year Slaty-backed Gulls must also be considered, but they tend have brownish and pale-edged primaries, and are stockier, and shorter legged than either Herring Gull. The Pribilofs offers an almost unparalleled opportunity for studying these three forms of often very similar gulls.