Factsheet

Cormorant

Cormorants are members of the pelican family.

Overview

Cormorant © Charles Lam CC BY-SA 2.0Distribution: Coasts around Great Britain and rest of Europe, Africa, Asia, eastern North America & Australia; often seen inland around lakes and rivers.

Habitat: Mainly marine but regularly seen on inland waters in many areas, even when breeding.

Description: Large, fairly long-necked bird, browny-black above, bluish-black below. White patch on chin & sides of face. White thigh patch in breeding season. Immature bird is brownish with paler underparts.

Size: About 90cm in length.

Food: Mainly fish, some molluscs & crustaceans.

Daily Life

Cormorants swimming © Charles Lam CC BY-SA 2.0Daily Life: Cormorants are rarely found far out to sea, preferring to fish near to the coastline and perch on rocks, jetties, cliffs or trees. They often go out feeding together, flying in lines, then settling on the water in a tight bunch. They swim around, ducking their heads beneath the surface to look for fish. When one bird dives, the others follow it. Fish are brought to the surface and swallowed head first.

Cormorants are expert swimmers, floating low in the water, sometimes with only their head and neck showing. To dive, they jump up and plunge in head-first, or just sink beneath the surface. They may dive down as far as 100 feet and the longest recorded dive is of 71 seconds. Usually they stay under for less than half a minute, swimming about 20-30 feet below the surface.

Cormorants are strong fliers, flying rather like a goose, with neck stretched out, head held up and rapid wing beats. They can soar in air currents, but usually fly low over the water.

Breeding: Cormorants nest in colonies, sometimes numbering thousands of birds. The nests are usually built on rocky cliffs, rocky islets or sometimes by rivers and lakes, even in trees. The nest is large and bowl-shaped, built of twigs, grasses, seaweed or reeds and becomes plastered with the birds' droppings. During courtship, cormorants wave their long necks about and the female may bend her neck right over her back. 2 - 4 eggs are laid and are incubated by both parents for about a month. The newly-hatched young are naked and have skins like black leather but later grow a curly, dark grey down. They are fed once a day by each parent with regurgitated fish; the chicks take this by pushing their heads down their parent's gullet. The chicks leave the nest and can fly in 5 - 8 weeks.

Cormorant drying wings © Tony Hisgett CC BY 2.0Wings hanging out to dry?: Cormorants are often seen perching on a rock or jetty with their wings outstretched. It is often assumed that a bird in this posture is drying its wings because they are not well waterproofed. However, this would be surprising in a bird which spends so much time in the water and it can be seen holding its wings open in the pouring rain! A more likely explanation for this habit is that it keeps a group of birds spaced out. When a bird lands, it extends its wings so that the birds nearby shift away; when it folds its wings the line of birds is well-spaced with a wingspan between each one. Being spaced out is also an advantage when taking off in a hurry.

Cormorants and Humans

Cormorants have sometimes been persecuted by fishermen because of the belief that they eat huge quantities of fish, especially in rivers where they were supposed to prefer young salmon and trout. However, research has shown that cormorants seem to favour flat fish and eels, taking only small amounts of the more saleable fish.

In the Far East, some fishermen make use of the cormorant's expertise, by training it to catch fish for them. A collar and lead is attached to the bird's neck and the collar is just tight enough to prevent the cormorant from swallowing a captured fish. The fisherman retrieves the fish from the bird's beak, only loosening its collar now and then to allow it to swallow a fish.

As with many sea birds, cormorants are affected by oil pollution, caused by shipwrecks or by ships which discharge their oil at sea illegally. Diving birds such as guillemots, razorbills and puffins have been most seriously affected by oil pollution, but cormorants have also suffered when fishing in the location of an oil slick. Oil clogs their feathers, they are unable to fly and swim and, as a result, they drown. Birds may also die of poisoning if they swallow oil.

Credits

Image: Cormorant by Kelly Colgan Azar

Information sourced from:

Friends of Harrold-Odell Country Park (2015), Fact Sheet:  Cormorants [online], Available from:  
http://www.hocp.co.uk/downloads/HOCP_Cormorants.pdf [accessed 01/06/2015]

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