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Cory's Shearwater Calonectris diomedea

Cory's Shearwater by Ben Lascelles

Field marks: Large shearwater 46-53 cm (18-21 inches) head-to-tail length and similar in size to the Greater Shearwater. Our only shearwater with a yellow bill. Grayish brown with little demarcation and and 'featureless' plumage. Strong flyer with long, gliding arcs; even in a modest wind it seldom flaps its wings.

Common in the western North Atlantic during the warmer months (May-November) but much less common in tropical and sub-tropical waters. Fairly common spring transient of Bermuda. Uncommon migrant in the Gulf of Mexico and Bahamas where it occurs mostly in May and June. Reported from waters off Cuba and the Lesser Antilles.

Natural History: Trans-Atlantic migrant. This species feeds mostly at the surface and aggregates at Gulf Stream surface thermal fronts when off the Atlantic Coast. Although Cory's Shearwaters nest at a number of sites in the Eastern North Atlantic, most individuals occuring from the central Atlantic US to the Caribbean and Gulf of Mexico are immature and sub-adult birds from the Mediterranean.

    Birds from these two populations can be distinguished, but the differences are not easy to detect unless the bird is in the hand. Atlantic birds are larger and have a stouter bill. The underwing pattern is the best character at sea with the Mediterranean population (C. diomedea borealis) having a black 'hand' with more black at the base of the primary feathers. The Atlantic birds (C. d. diomedea) have a white 'hand,' but even experts have trouble making that distinction on a given photograph.

West Indian Breeding Seabird Atlas by Will Mackin and David Lee is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 United States License. Based on work at www.wicbirds.net. Permissions beyond the scope of this license may be available at www.wicbirds.net.

Suggested Citation: Lee, D. S., W. A. Mackin. 2012. Cory's Shearwater. West Indian Breeding Seabird Atlas <http://www.wicbirds.net/sosh.html>. Last Updated: _____. Date accessed: ______.

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February 24, 2012
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