Sooty Shearwater
Sooty Shearwater
Ardenna grisea
At a Glance
In calm weather the Sooty Shearwater flies low over the ocean with quick, stiff beats of its narrow wings; in windy conditions, it glides and scales effortlessly over the waves. Sociable at sea, it is often seen in gatherings of hundreds or even thousands, flying in long lines or resting in dense rafts on the water. Although it is often the most abundant seabird off the coast of California, the Sooty Shearwater nests only deep in the Southern Hemisphere, around Australia, New Zealand, and southern South America.
All bird guide text and rangemaps adapted from Lives of North American Birds by Kenn Kaufman© 1996, used by permission of Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Category
Gull-like Birds, Shearwaters and Petrels
IUCN Status
Near Threatened
Habitat
Coasts and Shorelines, Open Ocean
Region
Alaska and The North, California, Eastern Canada, Florida, Mid Atlantic, New England, Northwest, Southeast, Western Canada
Behavior
Flap/Glide
Population
13.000.000
Range & Identification
Migration & Range Maps
Adults from southern colonies move north rapidly in April and May, passing Atlantic Coast of North America mostly in late spring. Moves north on broad front in Pacific. Peak numbers off California in late summer, probably corresponding to southward movement. Some, possibly non-breeders, are present at all seasons off our Pacific Coast.
Description
18" (46 cm). W. 41 (104 cm). Best recognized by shape and typical shearwater flight action, flapping and gliding in calm weather, gliding and scaling more in wind. Dark all over with tapering forehead and thin black bill, and with ragged white area on underside of wing.
Size
About the size of a Crow, About the size of a Mallard or Herring Gull
Color
Black, Brown, White
Wing Shape
Long, Narrow, Pointed, Tapered
Tail Shape
Pointed, Rounded, Wedge-shaped
Songs and Calls
Silent at sea; a variety of cooing and croaking notes on breeding grounds.
Call Pattern
Flat, Undulating
Call Type
Odd, Raucous, Scream
Habitat
Open ocean. Widespread at sea, but concentrates around upwellings and over continental shelf in cooler waters, also where cold and warm water masses meet. May come close to shore if water is deep. Breeds on islands in southern oceans with soil for burrows or with suitable rock crevices for nest sites.
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Behavior
Eggs
One. White. Incubation is by both sexes, averages 52-56 days.
Young
Both parents feed young, visiting at night, feeding frequently when chick is small and less often as it matures. Finally young bird is abandoned, and it eventually leaves to go to sea. Period from hatching to departure from nest averages about 97 days. Young usually departs from island at night.
Feeding Behavior
Forages by plunging into water from a few feet above the surface and swimming underwater, propelled by wings; also dives from surface, and seizes items at or just below surface while sitting on water. Sometimes feeds in association with whales, dolphins, and other seabirds.
Diet
Mostly fish, crustaceans. Diet in North Pacific mainly small fish, also euphausiid shrimp and other crustaceans, squid, jellyfish. In North Atlantic may feed mostly on euphausiid shrimp and fish.
Nesting
In Australia and New Zealand, nesting season is September to May. First breeding at age of 5-9 years. Breeds in colonies on islands, with most activity in evening and at night. In courtship, pairs may call in duet. Nest: Site is in burrow dug in soil, sometimes in natural crevice in rock. Burrow may be up to 10 feet long. Nest is loose foundation of leaves and grass.
Climate Vulnerability
Conservation Status
Abundant, with total population recently estimated at about 20 million, but numbers are declining in many areas. Has disappeared from some former nesting islands because of habitat degradation. In southern New Zealand, some young are taken annually for food and oil by Maori people, but this controlled harvest has little or no impact on total population. In recent years, off parts of North American west coast, numbers of visiting Sooty Shearwaters have declined significantly; this may be related to a general rise in sea surface temperatures there.