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The sooty shearwater has dark gray-brown plumage that looks almost black up close and is somewhat lighter on the underside. Its wings have a silvery lining, and it has a long, blackish-gray bill. An average-sized member of the shearwater family, individuals average 15-20 inches in length, have a wingspan of up to 43 inches, and weigh less than 1.5 pounds. Both sexes are similar in color and size, and chicks are generally smaller versions of their parents.
Distribution and Habitat
One of the most widespread of all seabirds, the sooty shearwater is found on all the oceans of the world. It spends most of the year far from land, but breeds in huge colonies on islands off New Zealand, Australia, southern Chile, and Argentina. Some populations are known to migrate over 40,000 miles a year between their feeding grounds in the northern oceans and their breeding grounds and back.
Breeding pairs typically stay together for life, although it is not known whether either partner will seek a new mate if the other one dies. Huge flocks containing 2.5 million or more pairs begin arriving at the breeding grounds toward the end of September, and egg-laying usually begins in mid-November. Individual birds that have recently become sexually mature spend the intervening time courting each other and forming into breeding pairs.
The nest is a burrow under grass or low scrub that may be up to 10 feet long. The single egg is incubated by both parents for about 53 days, and the chick is fed by both parents until fleging at about 97 days of age. The breeding colonies typically begin breaking up in late-April or early-May.
The sooty shearwater feeds on fish, crustaceans, and cephalopods. The bird hunts by flying low over the open water and either snatching prey from the surface or plunging into the water and pursuing prey under water. When under water, it beats its wings for propulsion and can reach a depth of over 200 feet before having to resurface.
Outside of the breeding season, sooty shearwaters are usually found in loose flocks of up to 50 individuals. They are usually quiet in flight, but are quite noisy when ashore. Their most common calls are der-rer-ah and coo-roo-ah.
Although still widespread in distribution, the sooty shearwater has experienced some population declines in parts of its range and is considered a near threatened species. The most common hazard faced by the species is long-line fishing, which uses lines of hooks that may stretch for miles behind the boats. The birds attempt to take the bait off the hooks but end up getting caught by the hooks and dragged underwater instead. In New Zealand, sooty shearwater chicks are taken by the native Maori.
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This page was last updated on October 31, 2017.