Cormorants also known as shags are a family of aquatic birds.
There are about 40 different species of cormorants.
They are distributed worldwide, with the largest diversity in tropical and temperate zones.
Cormorants inhabit marine and inland waters. They are found along marine coastlines of continents and islands. Inland populations inhabit lakes, open swamps and marshes, and rivers.
They live up to a maximum of about 25 years.
Cormorants and shags are medium-to-large aquatic birds. They range in size from the pygmy cormorant, at as little as 45 cm (18 in) and 340 g (12 oz), to the flightless cormorant, at a maximum size 100 cm (39 in) and 5 kg (11 lb).
The majority, including nearly all Northern Hemisphere species, have mainly dark plumage, but some Southern Hemisphere species are black and white, and a few are quite colorful.
Cormorants have special feathers, which allow the water to penetrate, enabling the bird to swim well under water.
The bill is long, thin, and sharply hooked. Their feet have webbing between all four toes, as in their relatives.
Cormorants have short wings for a flying bird due to their need to swim. Because of this they have the highest flight cost of any flying bird.
Some species of cormorants can attain speeds of up to 55 kilometers (34 miles) per hour.
Cormorants are expert divers, dive up to 4 minutes looking for food. Some types of Cormorant diving as deep as 45 meters (148 feet). They speed along underwater via their webbed feet, using their wings as rudders.
Some cormorant species are migratory, whereas others are sedentary.
All are fish-eaters, dining on small eels, fish, and even water snakes. They dive from the surface, though many species make a characteristic half-jump as they dive, presumably to give themselves a more streamlined entry into the water.
Many species hunt together.
After fishing, cormorants go ashore, and are frequently seen holding their wings out in the sun.
Cormorants are colonial nesters, using trees, rocky islets, or cliffs. Colonies range in size from a few to 2,000 pairs.
They are considered seasonally monogamous. The male chooses the nest site and then attracts a female. Nests can be on the ground, on rocks or reefs with no vegetation or atop trees.
The eggs are a whitish color. There is usually one brood a year. The young are fed through regurgitation. They typically have deep, ungainly bills, showing a greater resemblance to those of the
pelicans, to which they are related, than is obvious in the adults.
Cormorants seem to be a very ancient group, with similar ancestors reaching back to the time of the dinosaurs. In fact, the earliest known modern bird, Gansus yumenensis, had essentially the same structure.
The name cormorant is derived from the Latin corvus marinus, which means “sea crow”.
Humans have used cormorants’ fishing skills in various places in the world. Archaeological evidence suggests that cormorant fishing was practiced in Ancient Egypt, Peru, Korea and India, but the strongest tradition has remained in China and Japan, where it reached commercial-scale level in some areas.
In a common technique, a snare is tied near the base of the bird’s throat, which allows the bird only to swallow small fish. When the bird captures and tries to swallow a large fish, the fish is caught in the bird’s throat. When the bird returns to the fisherman’s raft, the fisherman helps the bird to remove the fish from its throat. The method is not as common today, since more efficient methods of catching fish have been developed, but is still practiced as a cultural tradition.
Cormorants feature in heraldry and medieval ornamentation, usually in their “wing-drying” pose, which was seen as representing the Christian cross, and symbolizing nobility and sacrifice.