This is a medium-large black bird, 68-78 cm long and with a 95-110 cm wingspan. It has a longish tail and yellow throat-patch. Adults have a small crest in the breeding season. It is distinguished from the Great Cormorant by its smaller size, lighter build, thinner bill, and, in breeding adults, by the crest and metallic green-tinged sheen on the feathers. Among those differences are that a shag has a lighter, narrower beak; and the juvenile shag has darker underparts. The Shag's tail has 12 feathers, the Great Cormorant's 14 feathers. The green sheen on the feathers results in the alternative name `Green Cormorant`.
Habitat and Distribution
It breeds around the rocky coasts of western and southern Europe, southwest Asia and north Africa, mainly wintering in its breeding range except for northernmost birds. It is rare inland. It will winter along any coast that is well-supplied with fish.
It feeds in the sea, diving to at least 45 metres and may find prey on the bottom of the sea. . They will eat a wide range of fish but their commonest prey is the sand eel.
They nest on rocky ledges or in crevices or small caves. The nests are untidy heaps of rotting seaweed or twigs cemented together by the bird's own guano. The nesting season is long, beginning in late February or later. Three eggs are laid. Their chicks hatch without down and so they rely totally on their parents for warmth, often for a period of two months before they can fly. Fledging may occur at any time from early June to late August, exceptionally to mid October.