Seabird colony

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Great Frigatebirds, Black Noddies and Red-footed Boobies nest on bushes while Red-tailed Tropicbirds and Sooty Terns nest on the ground around and underneath them (French Frigate Shoals, Hawaii).

Common Murre colony (Farallon Islands).

A seabird colony is a site which seabirds visit to breed, typically during the summer. Although some colonies are small, classic seabird colonies contain hundreds or thousands of birds (some colonies of over a million birds are known). Colonies are usually at coastal locations (e.g. cliffs, lagoons, islands, beaches), although some birds traditionally regarded as seabirds have spread and founded colonies inland. In addition, some nocturnal petrels and shearwaters nest inland on mountains or cliffs.

Individual nesting sites at seabird colonies can be widely spaced, as in an albatross colony, or densely packed like an auk colony. In most seabird colonies several different species will nest on the same colony, often exhibiting some niche separation. Seabirds can nest in trees (if any are available), on the ground (with or without nests), on cliffs, in burrows under the ground and in rocky crevices.

The species makeup of a seabird colony depends on its topography and geography. Cliff colonies in northern latitudes are usually dominated by auks and kittiwakes. Particularly large colonies of this type occur in the north Atlantic, such as in Britain, Ireland, Norway, Newfoundland and Iceland; and in the north Pacific, particularly Alaska, Kamchatka, the Kuril Islands and the Sea of Okhotsk. Colonies on tropical islets are usually dominated by terns, for example at the Dry Tortugas.

Many seabirds show remarkable site fidelity, returning to the same burrow, nest or site for many years, and they will defend that site from rivals with great vigour. This increases breeding success, provides a place for returning mates to reunite, and reduces the costs of prospecting for a new site. Young adults breeding for the first time usually return to their natal colony, and often nest very close to where they hatched.

Colonies are thought to provide protection to seabirds, which are often very clumsy on land, and are usually situated in places combining inaccessibility to land mammals and access to productive nearshore feeding grounds.

Colony size is also often claimed to covary positively with pathogen pressure.