Cormorants are extremely social birds. They live together in colonies which, during the breeding season, include several hundred pairs. During the winter then the tendency to cohabitation is further accentuated and the birds gather in thousands along the rivers or on the large expanses of water obtaining many advantages: greater profitability in fishing, reinforcement of the cohesion of the groups and solicitation of nuptial behaviour.
Avian flu is one of the dangers that is slaughtering them. To this must be added the climate and environmental crisis. At night, the cormorants gather by the hundreds or thousands in the resting places, the dormitories, made up of the large trees that line the rivers, forming
clusters of birds that alight there from sunset until late at night.
At the end of winter, a clearly visible trace remains of this stay: the whitish crust made up of bird droppings. These birds, which prefer sheltered seas, avoid deep waters even close to the mainland and rarely move away from the shores: they can be seen on lakes, basins, deltas, estuaries, large waterways, generally when the current is weak, more rarely if they are torrents.
Cormorants spend a lot of time on land, roosting on rocks, cliffs, sandbars, natural and artificial barriers Fish form the essential basis of the cormorants' diet, which however spend only 20% of their day fishing, preferably in the morning and early afternoon: the search for food usually ceases long before sunset.
Hunting trips are interrupted by frequent pauses, during which the cormorants rest and, stationary on sand or mud banks, rocks, dams, wait for their feathers to dry. Primarily an aquatic animal, mostly linked to both salty and fresh waters, the common cormorant lives on all continents except in South America.
It nests in the extreme north-east of the United States, in Newfoundland and in Greenland; in Europe, from northern Norway to the Mediterranean basin. In Asia, it is present up to India and China; in Japan, only the island of Honshū hosts a subspecies of it.
Elsewhere, it is encountered in East Africa and Southeast Asia. Another subspecies inhabits Australia, Tasmania, New Zealand and the Chatham Islands.