Cormorant vs Shag: How to Tell Them Apart

This bird is the size of a big goose and has a green eye, a large bill with a hooked tip, a broad neck and a graded forehead. The sexes are similar but there is some difference in plumage across the seasons. The summer adult is dark, with black-bordered brownish wing feathers in good light. It has yellow at the bill's base which fades to white. In spring it has patches of white on the thigh, head and neck; the winter birds lose these white feathers. Juvenile birds have brown upperparts and pale underparts, and they accumulate adult plumage over two years.

Breeding sites are formed during spring and summer around rocky cliffs and islands in Ireland and the south, west and north of Britain. Increasingly found near lakes and rivers too, where they're more likely to build nests in trees.

It's vocal at breeding colonies; deep, nasal sounds such as 'agock-agock-agock' are made by adults. Predominately quiet at other times.

This bird is similar to the Cormorant in many ways, but it is more slight and its hook-tipped bill is narrower; its head is smaller, the angle of the forehead leading to the crown more acute. The sexes are similar, though plumage differs across the seasons. In summer, the adult is a dark greenish-black, the green and even purple are brought to life in the right light, it has a yellow patch at the bill's base and a distinctive crest. In winter adults the yellow at the base of the bill is faded, the plumage is browner, the throat is pale, and the crest is lost. Juvenile birds are brown, without the light underparts the juvenile Cormorant has, though the throat is pale.

Strictly a marine bird, the Shag seems to enjoy environments with turbulent seas. It breeds on rocky coasts of the region, north and west Britain and along the south coast to the Isle of Wight, where it creates nests on seaside cliffs.

When in nesting colonies it utters a series of harsh grunts and clicks.