The great shearwater is a large seabird, similar in size to the fulmar but recognised by its darker plumage overall. It is a long-distance migrant that breeds on a small number of South Atlantic islands, including Nightingale Island, Inaccessible Island, Tristan da Cunha, and Gough Island. In the UK, it is a rare summer visitor, but occasionally appears in its hundreds or even thousands as it follows its circular migration route.
The great shearwater is among the seabird species most severely affected by plastic ingestion.
Migrant birds: Not known
Family: Shearwaters And Petrels
The great shearwater has grey-brown upperparts with pale-edged feathers, creating a scaled appearance. Its uppertail coverts are white, forming a crescent shape at the base of the tail, while the tail feathers (rectrices) are dark brown.
The underparts are predominantly white, with a pale brown patch on the belly that can sometimes appear mottled. The flight feathers are white with dark grey edges, and the lesser and median underwing coverts are marked with dark spots and stripes.
The head has sooty brown colouring on the crown, upper face, back of the head, and nape, while the chin and throat are white. A distinctive white collar encircles the neck. The bill is dark grey, the eyes are dark brown, sometimes framed by a white eyering, and the legs and webbed feet are pink with black toes.
Males and females are similar in appearance, although females tend to be smaller with shorter wings.
Juvenile great shearwaters resemble adults but lack the white neck collar.
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The great shearwater breeds in October and November, producing one brood per season. It is monogamous, forming long-term pair bonds, and nests in colonies in areas with tussock grass, ferns, small trees, and shrubs. The nest is a burrow in a grassy slope, excavated by both the male and female using their feet and beaks, with no additional material added.
Each pair lays a single white egg, which is incubated by both parents for 56 days. To minimise the risk of predation by large gulls, the nests are only visited at night. The chick, covered in grey down, is fed by both parents and fledges between 105 and 120 days after hatching. Great shearwaters reach sexual maturity at three to five years of age.
The great shearwater is gregarious and often feeds in large, noisy flocks. Its diet consists of squid, fish, and crustaceans, which it catches through pursuit-plunging from heights of 6–10 metres above the water, with each dive lasting around 10 seconds. It also feeds by foraging from the surface, and may follow trawlers to scavenge discarded fish offal, entrails, and crustaceans.
Great shearwaters can be spotted between August and October, only offshore along the north and west coasts of Scotland and the southwest coast of England. For the best chance of seeing them, watch from headlands during onshore winds.
Great shearwaters are one of the few species of birds to migrate from its breeding grounds in the Southern Hemisphere to the Northern Hemisphere for winter.
