Shag

The shag (Phalacrocorax aristotelis) needs to be distinguished from its larger cousin the cormorant, despite Christopher Isherwood’s famous line: “The common cormorant, or shag, lays eggs inside a paper bag.” Isherwood was wrong on both counts! The confusion is easy to make, however, given that the two species have much in common and are sometimes found together in joint colonies.

  

Habitat

The shag is a coastal bird, preferring to inhabit rocky coasts and islands. It is found in Europe anywhere from Norway and Iceland to the Mediterranean. In the British Isles it breeds at several sites around the Scottish coast, such as in the northern and western isles, and it is also found in Ireland, Wales and the south-west peninsula of England.

Appearance

The shag is around 75 centimetres (30 inches) in length. It has a slender bill, a long neck, thinner than that of the cormorant, and a forehead that is steeper. It also displays a prominent crest in Spring. The summer plumage, which is similar as between males and females, is glossy-green to black with a purple sheen on parts of the wings. The bill is black with a yellow base and the eyes are green. In winter the plumage is less glossy.

Behaviour

The shag is a strong flyer, with glides and fast wing-beats. It feeds by diving to depths of up to twenty metres.

Shags feed mainly on fish, but will also take crustaceans and molluscs.

When nesting, shags communicate with throat clicks, and at other times produce a loud rasping croak. In addition, male shags grunt and females hiss.

Breeding

Shags nest in looser colonies than cormorants, the nest comprising seaweed, grass or leaves, plus a few twigs, on a rocky ledge which might be inside a sea cave. The clutch, only one of which is laid in a season, is of anything from two to six eggs, laid at any time from mid March to August. These are incubated by both partners, for up to 32 days.

The young birds demand food from virtually as soon as they hatch, and the parents oblige three to four times daily. The young shags feed by thrusting their heads into their parents’ throats for regurgitated fish. They leave the nest for the water at around 50 days, although not yet able to fly. This takes a week or 10 days longer.

Young shags have a high mortality rate, with up to 80% unlikely to survive their first year. Threats include predators such as great skuas, the numbers of which are currently rising in Scottish coastal waters.

Shags disperse from their breeding grounds between September and March but are unlikely to go very far. Unlike cormorants, shags rarely winter inland.

Conservation

Shags have amber list conservation status in the United Kingdom, mainly because their breeding sites are relatively limited. Over half the total number of birds is found at fewer than ten sites.

© John Welford