The refuge has a surface area of 22 acres (0.089 km2).[1]
Wildlife & Habitat
Thacher Island is home to herring and great black-backed gulls. The refuge serves as a stopover site for songbirds and other migrants to rest and feed during their seasonal migration. Off-shore habitats are used by seals, waterfowl, loons, grebes, cormorants, and alcids.
Historically, the island served as nesting grounds for several species of terns, but over the years it has been overrun by the gulls. Still, Thacher Island has the potential to be re-established as a prime nesting area. The habitat remains ideal for tern breeding. Nesting terns are currently supported on islands strategically located to the north and south of the Thacher Island, and could be attracted to re-establish nesting colonies on the island.