Boobies and Gannets

The northern gannet (Morus bassana) breeds in north-temperate and subarctic waters on both sides of the Atlantic Ocean. In North America, the largest colonies of these birds occur at Cape Saint Mary's on Newfoundland and on Bonaventure Island in the Gulf of the Saint Lawrence River. There are another four smaller colonies of northern gannets in the western Atlantic Ocean and another 28 in the eastern Atlantic.

Adult northern gannets have a white body, with black wing-tips. The head is a bright lemon-yellow. During the first year after birth gannets are a dark-brown color, while older sub-adults have a dirty-white plumage and lack the yellow head of the sexually mature adults. The tail of gannets is pointed, as is the profile of their head, giving the bird a double-ended shape in flight.

The populations of northern gannets in some of their breeding colonies can be quite large. These birds are aggressively territorial, and their nests are therefore spaced at about twice the distance that a sharp beak can be thrust towards a neighbor. Other displays involve birds engaging in ritualized posturings to impress their neighbors, or to infatuate a potential mate.

In healthy colonies, all of the suitable space may be covered with nests. At Cape Saint Mary's, population growth in recent decades has resulted in all of the prime nesting habitat on cliffs to be fully utilized. This has forced many birds to nest on adjacent coastal meadows, an accessible habitat in which they are vulnerable to land-borne predators.

After their breeding season, northern gannets occur widely in waters of the continental shelves. During the winter, gannets range as far south as the northern Gulf of Mexico and the southeastern United States.

Other species of gannets include the Cape gannet (Morus capensis) of South Africa, and the Australian gannet (M. serrator) of Australia. These species are rather similar to the northern gannet, and some taxonomists consider all of these taxa to be subspecies of Morus bassana.