Cory's Shearwater

Cory's Shearwater is one of the largest shearwater species, with a bulky, gull-like build that can make it look surprisingly heavy in flight compared to smaller relatives. It has brownish-grey upperparts that blend gradually into white underparts, without the sharply contrasting black-and-white pattern seen in many other shearwaters, along with a stout, pale yellowish bill.

The species breeds in large colonies on islands scattered across the eastern North Atlantic, including the Azores, Canary Islands, Madeira, and Mediterranean, nesting in burrows and rock crevices that it visits only at night to avoid predators.

At sea, Cory's Shearwater has a distinctive, relatively slow and languid flight style, with long glides on bowed wings low over the water, differing from the stiffer, faster wingbeats of many smaller shearwater species.

Key field marks

• Large size with brownish-grey upperparts blending softly into white underparts
• Stout, pale yellowish bill
• Slow, languid flight with long glides on gently bowed wings

Similar species

• Great Shearwater has a more sharply demarcated dark cap, a white collar, and a dark bill, unlike Cory's more uniform grey-brown head and pale bill.
• Scopoli's Shearwater, a very close relative sometimes considered the same species, shows more white in the underwing and is best separated with careful observation.

Cory's Shearwater breeds on islands across the eastern North Atlantic and Mediterranean, with major colonies in the Azores, Canary Islands, and Madeira. Nests are built in burrows, rock crevices, or under boulders on rocky or vegetated slopes, visited only under cover of darkness.

Outside the breeding season, the species migrates across the Atlantic, with substantial numbers wintering in productive waters off South America and southern Africa before returning to their Atlantic island colonies to breed.

Voice

At night around breeding colonies, Cory's Shearwaters give loud, wailing, and cackling calls exchanged between pairs and rivals, audible from within nesting burrows.

Feeding

They feed on fish, squid, and crustaceans, caught by surface-seizing, shallow plunge-diving, and occasionally following fishing vessels or feeding alongside marine mammals and tuna schools.

Nesting and breeding

Pairs nest in burrows or natural rock cavities, returning to the same site each year, and lay a single egg. Both parents share incubation duties, with adults commuting to and from the colony only at night to avoid predation.