Cormorant

The cormorant (Phalacrocorax carbo) needs to be distinguished from its smaller cousin the shag, despite Christopher Isherwood’s famous lines that begin: “The common cormorant, or shag, lays eggs inside a paper bag.” Isherwood was wrong on both counts; it isn’t, and it doesn’t.

The cormorant is a very familiar seabird all around the coasts of the UK and Ireland, and many other parts of the world besides. When you see a cormorant standing with its wings outstretched to dry them, it is not difficult to see how birds could have evolved from reptiles; the shape the cormorant makes is not wholly unlike that of the archaeopteryx, the most primitive, but long extinct, bird-like creature known to science.


Appearance and behaviour

The cormorant is about 90 centimetres long (36 inches), with a long neck and heavy bill (much heavier than that of the shag). The summer plumage of adult birds (both male and female) is blue-black and glossy, but with white on the cheeks and throat and a patch on the thigh. The upper parts of the wings are bronze in colour with black edges to the feathers. The plumage changes in winter to be less glossy, with brown mottling on the white areas, except for the thigh patches which disappear completely. The bill is green and yellow and the eyes are green.

Cormorants can often be seen in groups, such as on groynes extending out to sea, or one on each of a series of wooden posts that are the remains of a sunken boat in a coastal lagoon or estuary mudflat. These lines of black, reptilian birds are what have given the cormorant the reputation of being sinister harbingers of misfortune, the marine equivalent of vultures waiting for a meal.

However, when not at rest, cormorants can be seen flying at speed, low across the water, or diving from the surface for fish, which comprise most of their diet. Taking off from the surface is not easy for them and involves a lot of wing flapping and noise. They sometimes feed in groups of around eight birds, corralling the fish into shoals which they can pursue more easily. They will also feed on crustaceans and are especially fond of crabs.


Breeding

Breeding usually takes place from April to June (but sometimes as late as August), in large colonies on rocky islands or cliffs, or in trees (often dead ones) further inland. They are quite likely to use old nests as the foundations of new ones, these comprising woven twigs or grass stems, depending on the availability of material. Both partners build the nest, after which the female lays three to five eggs that take around 25 days to hatch, with both parents incubating them. Cormorants only have one brood per season.

The chicks are blind for the first three days after hatching. They take food from their parents’ throats, staying in the nest for up to 55 days, after which they form large flocks with other young and adult birds.


Conservation

Because of their appetite for fish, cormorants are not always popular with the angling and fishing fraternities, and there has been some persecution of cormorant populations in the past. However, the main threat to cormorants in British waters is sudden depletions of fish stocks, for whatever reason. A large number of cormorants in an area is an indication that there are plenty of fish around.

Further information about the cormorant, including a recording of its call, can be found on this page of the RSPB website.

© John Welford