Great Shearwater: Large shearwater, scaled, gray-brown upperparts, white underparts, brown markings on belly. Dark cap contrasts with white face. Tail is dark above with conspicuous white rump band and gray below. Dark, hooked bill. Pink legs, feet. Flies on deep wing beats followed by long glide.
Range and Habitat
Great Shearwater: This species breeds on the islands of Tristan de Cunha in the southern Atlantic Ocean. They are migratory, and spend May to early November as a nonbreeding visitor to the north Atlantic and may occur along the Atlantic Coast of North America from Florida to Canada. They may also wander into the Gulf of Mexico. They are pelagic, only coming ashore to breed.
Petrels and Shearwaters (Procellariidae)
There are four families of seabirds in the PROCELLARIIFORMES (pronounced pro-sel-lehr-EYE-ih-FOR-meez), an order that includes the dainty storm-petrels, the huge albatrosses, and the shearwaters.
The shearwaters are in the Procellariidae (pronounced pro-sel-lar-EYE-ih-dee), a family composed of eighty-five species in fourteen genera that roam all oceans of the world.
In North American waters, thirty-five species of shearwaters in six genera have been identified. Included among these are the thin-winged Pterodrama species of the deep waters such as the Black-capped Petrel, and the stocky, gull-like Northern Fulmar.
Shearwaters are known for the prominent tube-like structures on their beaks that, as with all Procellariiformes, help remove excess sea water. Species such as the Sooty and Short-tailed Shearwaters are also known for their open water, low altitude gliding and tilting mode of flight on straight wings, the tips of which often slice or “shear” through the water’s surface.
Shearwaters are seabirds that are medium to large in size with elongated round bodies, medium length tails, long, pointed wings, and webbed feet adapted to their marine environment. Their bills are medium length, narrow, have a small hook on the tip, and are topped with tubular nasal structures.
This dull-colored family is plumaged in dark browns, black, white, and gray. Some species such as the Sooty Shearwater are all dark with silvery wing linings, while others such as the Great Shearwater are dark above and light below. The Black-capped Petrel and related species have gray and white plumage with bold black markings on the head, back, and wings.
Shearwaters are encountered in deep, marine waters off of both coasts with the deepest waters beyond the continental shelf favored by the petrels of the Pterodrama genus. They only occur on fresh water if blown inland by hurricanes, and on land are only likely to be encountered on northern cliffs and islets that are their breeding grounds.
Some species undertake very long migrations from breeding areas in the Southern Hemisphere to the waters of the Northern Hemisphere.
Shearwaters nest in colonies, and often occur in flocks when foraging. Fish, squid, crustaceans, and other food items are sometimes picked from the surface, but mostly obtained by diving into the water.
Populations of several species of shearwaters have been declining with subsequent listing as near-threatened or threatened; these declines likely linked to long-line fishing and global warming. Shearwaters are also easily threatened by disturbances at their breeding grounds.
Shearwaters produce an oily substance in their stomachs that is fed to young and which can be vomited as a defense mechanism. Young birds high in fat and oil content are harvested by the Maori people in New Zealand where they are called, “muttonbirds”.