The Great Shearwater (Ardenna gravis) is one of the greatest travelers in the avian world. This seabird completes an astonishing migration each year, crossing the Atlantic from end to end. With a respectable size, it is perfectly adapted to a pelagic life, spending almost its entire existence on the high seas. Its sighting is always an event for ornithologists, offering a glimpse of the endurance and wild beauty of the oceans.
By the Les-Oiseaux.com team, published on August 03, 2025.
My personal advice: To identify the Great Shearwater, focus on the head. The most reliable feature is its very sharp, dark brownish-black cap, which extends below the eye and contrasts sharply with the white throat and an almost complete white collar on the back of the neck. This dark "helmet" immediately distinguishes it from the Cory's Shearwater, which has a grayer, more blended head.
In flight, also look for the white 'V' or crescent on the rump, just before the dark tail. Although sometimes inconspicuous, this detail is an excellent clue. Finally, its flight is powerful and direct, alternating between a series of rapid wingbeats and long glides close to the waves, with wings held stiffly. It appears less bulky than the Cory's Shearwater and is significantly larger than the Manx Shearwater.
The Great Shearwater is a good-sized bird. Its plumage is a play of well-defined contrasts.
Juveniles look very similar to adults, with simply newer plumage and a slightly grayer rather than brown overall appearance.
At sea and during its migration, the Great Shearwater is generally a silent bird. It is on its distant breeding grounds that it becomes noisy, especially at night. The colonies then echo with a variety of calls, described as high-pitched hoots, wails, or nasal bleating sounds. When squabbling over food in groups, it may emit harsh, discordant squawks.
The Great Shearwater is a gregarious bird, often forming large rafts of several hundred individuals at sea to rest or feed. Its most remarkable behavior is its migration. After breeding in the Southern Hemisphere, it begins a long journey north in April, following the coasts of the Americas to reach the rich waters of Canada and Greenland in the summer. At the end of summer, it crosses the Atlantic eastward and descends towards its nesting sites, passing offshore of Europe and Africa. It is an excellent glider, capable of using winds to cover vast distances with minimal effort.
To feed, it catches fish and squid by plunge-diving from the air or by picking them from the surface. It is known to follow fishing boats and marine mammals, taking advantage of feeding opportunities.
Confusion is possible with the Cory's Shearwater (Calonectris borealis), another large shearwater of the Atlantic. The Great Shearwater, however, is more slender and is distinguished by specific features.
| Feature | Great Shearwater | Cory's Shearwater |
|---|---|---|
| Head | Sharp brownish-black cap, contrasting with a white collar. | Grayish head and neck, gradually blending into the back. |
| Bill | Thin and entirely black. | Robust, pale yellow with a darker tip. |
| Rump | Clearly visible white V-shaped or crescent band. | Pale rump but without a clean white mark. |
| Flight | Powerful, direct, with stiffer wingbeats. | More leisurely and flexible flight, with longer glides. |
The Great Shearwater is a purely pelagic bird outside the breeding season. It only comes to land to nest, and does so on a very limited number of islands in the South Atlantic. The main colonies are found on the Tristan da Cunha archipelago (Inaccessible, Nightingale, and Gough Islands) and on Kidney Island in the Falkland Islands. It is here that it digs its burrow in grassy slopes.
The rest of the year, it roams the vastness of the Atlantic Ocean. Its migration takes it as far as the Arctic Circle. A large part of the world's population spends the non-breeding period (our summer) in the Canadian waters of the Northwest Atlantic.
Globally, the Great Shearwater is listed as "Least Concern" (LC) by the IUCN, due to its still very large global population, estimated at at least 15 million individuals. However, the species faces serious threats. Accidental bycatch by longline fisheries is a known cause of mortality. Furthermore, like many seabirds, it is particularly vulnerable to ingesting plastic debris, which it mistakes for food. Protecting its nesting sites and reducing plastic pollution in the sea are crucial for its future.
The Great Shearwater is famous for its spectacular trans-equatorial migration. Every year, it completes a huge loop in the Atlantic Ocean, moving from its breeding grounds in the Southern Hemisphere (like Tristan da Cunha) to the rich feeding areas of the North Atlantic, before returning south along the coasts of Europe and Africa.
The main distinction lies in the head and bill. The Great Shearwater has a well-defined black cap that contrasts with a white collar and a thin, all-black bill. The Cory's Shearwater, on the other hand, has a grayer head and neck and a robust, pale yellow bill with a dark tip.
It is a pelagic bird that spends most of its life on the open ocean. The best chances to see one are during seawatching trips, especially during its migration. It is regularly seen off the coast of North America in summer and passes offshore of Western Europe mainly in the fall during its southward migration.
Its diet consists mainly of fish, squid, and crustaceans. It is also known to follow fishing boats to feed on discards and often associates with marine mammals.
No, they are two different species. The Manx Shearwater (Puffinus puffinus) is significantly smaller and more contrasted, with a black back and bright white underparts, and it lacks the distinct dark cap and white rump of the Great Shearwater.