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. Occurrence: 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
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
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.
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.
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: ______.