What predators eat antarctic terns?

Arctic terns feed by diving and snorkeling, searching for a variety of small fish, crustaceans, and other invertebrates, as well as catching flying insects. In some areas, aquatic insects are their primary prey. When they nest with common terns (Sterna hirundo), they feed on more invertebrates than the latter. As with other Arctic species, the breeding season is short, with Arctic terns spending only two to three months in their breeding grounds. Within their extensive Arctic breeding range, many nest widely across the tundra or in small colonies on lake islands. Others congregate in dense colonies on coastal islands. In the southern part of their breeding range in the Atlantic Ocean, Arctic terns interbreed with common terns. Distinguishing between these two very similar species is challenging. Outside of the breeding season, the Arctic tern is one of four or five bird species frequently seen on the Antarctic ice sheet; however, it is rarely observed by most visitors to the continent. Its biology has received little attention, but it could be key to understanding its peculiar lifestyle. 

In breeding areas, the North American Arctic tern has received less attention than the common tern, which exhibits very similar behavior. Comparative references are frequently cited in this report. Extensive studies conducted in Europe have been summarized in three reference guides (Glutz von Blotzheim and Bauer, 1982; Cramp, 1985a; Il'Icev and Zubakin, 1990). Further evidence summarizes information from Antarctica, as well as from the Australian region (Higgins and Davies, 1996). Two initial studies of breeding colonies were carried out on the Farne Islands, northeast of England (Collen, 1956; Collen, 1960a), and in the eastern Gulf of Main/Outer Bay of Fundy (Hocksley, 1957). Both locations are near the southern limit of the species' range. Comprehensive studies have also been published north of the Arctic Circle (in the White Sea, northwest of Russia, 67°N) (Bianchi, 1967). The notable lack of studies in the Arctic interior is attributed primarily to the species' wide distribution and the resulting difficulty in collecting sufficient specimens, although the fierce defense of its nest may also be a contributing factor.

Little is known about the current status of the Arctic tern, mainly due to its remote nesting areas and the dispersal of large populations. In southern New England, after recovering from the 19th-century slaughter for its feathers, its population in remote areas has recently declined to near extinction, while the common tern population has thrived.