Cory’s Shearwater
Cory's Shearwater
Calonectris diomedea
At a Glance
This species as a stronger flight action than most shearwaters, with slower wingbeats and prolonged glides, sometimes soaring high above waves. Nesting on islands in the Mediterranean Sea and eastern Atlantic, it regularly visits waters off the east coast of North America. Although a few get as far north as Canada, the species is most common off the southeastern states.
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
Least Concern
Habitat
Open Ocean
Region
Eastern Canada, Florida, Mid Atlantic, New England, Southeast, Texas
Behavior
Flap/Glide, Rapid Wingbeats, Swimming
Population
510.000
Range & Identification
Migration & Range Maps
Winters mainly off southern Africa. Breeding adults are generally near colonies from March to October, so birds seen off east coast of North America (peak numbers June to November) apparently are immatures and nonbreeders.
Description
20" (51 cm). W. 46 (117 cm). Large and long-winged, with slower wingbeats than other eastern shearwaters. Brownish gray above and whitish below, but colors smudge together, without strong contrast. Base of bill yellow.
Size
About the size of a Crow, About the size of a Mallard or Herring Gull
Color
Brown, Gray, White, Yellow
Wing Shape
Broad, Long, Rounded, Tapered
Tail Shape
Pointed, Rounded, Short, Wedge-shaped
Songs and Calls
Howling, gurgling calls heard only on breeding grounds.
Call Pattern
Flat, Undulating
Call Type
Raucous, Scream
Habitat
Open ocean. Favors relatively warm waters, warmer than those sought by Greater Shearwater. May occur farther north off North American coast in warm-water years. At least off southern New England, may be seen from shore more often than other shearwaters. Occurs both over continental shelf and far out to sea. Nests on islands, often rocky or mountainous.
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Behavior
Eggs
One. White. Incubation is by both sexes, 52-56 days.
Young
Both parents feed young, visiting at night. Eventually young is deserted and goes to sea on its own. Period from hatching to departure probably about 90 days.
Feeding Behavior
Forages mainly by plunging into water from just above surface, and by seizing items while swimming. Often may feed at night. Scavenges near fishing boats; may feed in association with whales or large predatory fish, which drive schools of small fish to the surface.
Diet
Mostly fish, squid, and crustaceans. Diet not well known; fish eaten include herring and sand lance. At times may feed mainly on squid. Also eats crabs and other crustaceans, and on scraps and offal around fishing boats.
Nesting
Breeds in colonies on islands; on large islands, colonies may be several miles inland. Breeding season mostly from March to October. Activity in colonies mainly late afternoon to dawn; where persecuted by humans or other predators, may visit colonies only at night. In courtship, members of pair sit close together on ground, nibbling at each other's head and bill. Nest: Site is in burrow up to 3' long, or in crevice in rocks, sometimes on ground under thick scrub. Nest is simple pile of pebbles, shells.
Conservation
Conservation Status
Still numerous despite declines in some nesting areas. Colonies are vulnerable to disturbance and to pollution of nearby waters.