Great cormorant

Great cormorants eat fish.

They dive under the water to catch them.

Great cormorants eat almost entirely fish, with some crustaceans (the group that includes crabs and shrimp), worms and other small animals. One study found them eating at least 22 kinds of fish. At sea they mostly catch fish that live near the bottom.

A cormorant dives underwater to catch fish. Most of its fishing happens within about 3 meters of the surface, but it can go much deeper. It fishes only in daylight, usually alone, though in some places large fishing flocks gather.

The IUCN lists a mainly fish diet, including sculpins, capelin, cod-family fish and flatfish, with crustaceans, amphibians, molluscs and nestling birds; at sea it takes mostly bottom-dwelling fish, and one study recorded at least 22 fish species (Gremillet 1997). Feeding is exclusively by day, usually alone, though large fishing flocks form in some areas.

Diving depths differ by source: Audubon's account (Kaufman 1996) puts most foraging within 3 meters (10 feet) of the surface, with dives to 9 meters (30 feet), while the IUCN says birds rarely dive below 10 meters but have been recorded at 35 meters. Most foraging trips stay within 10 kilometers of the colony, with some up to 35 kilometers (IUCN).

A male cormorant waves his wings to show off to a female.

Partners twist their necks together at the nest.

In the breeding season a male picks a nest site and tries to attract a female by waving his wings up and down, showing off white patches on his body. Once paired, the two birds greet each other at the nest by twisting and winding their necks together.

Cormorants also gather to rest together at regular roosting sites, near their nests or near good fishing places. They make deep, throaty grunts.

The male chooses the nest site and displays to attract a female by waving his wings up and down and flashing white rump patches; paired birds display at the nest by writhing and intertwining their necks (Audubon guide, Kaufman 1996). The call is a deep guttural grunt.

The species roosts communally at nesting sites or major feeding areas and flies in flocks of varying size; flocks of up to 890 birds were counted off eastern Jutland and Læsø, Denmark (Petersen et al. 2003, cited by the IUCN). The BTO notes that some individuals are remarkably faithful to their roosts over time.

There are lots of great cormorants.

In some places there are more now than before.

The great cormorant is listed as least concern, and its numbers have been increasing. In the UK, cormorants nested almost only on the coast until 1981, but they have since set up colonies in many inland areas of England. The number spending the winter in the UK grew by 46% from 1998 to 2023.

Because cormorants are expert fishers, they can come into conflict with people who fish, and in the past they were persecuted. Cormorants can also get caught by accident in fishing nets.

BirdLife International assessed Phalacrocorax carbo as Least Concern for the IUCN Red List (assessed 9 August 2018, published 2019 as an amended version): an extremely large range, about 1.4 to 2.1 million individuals worldwide (Wetlands International 2015), 401,000 to 512,000 pairs in Europe (2015), and an increasing trend. Because it dives in shallow water and hunts inside purse-seine and gill nets, it is particularly prone to bycatch, though this is not currently found to be driving colony declines (IUCN).

In the UK, the BTO reports that inland colonies spread after 1981, thought to have been sparked by the continental race sinensis from the Netherlands and Denmark, with 2,362 inland pairs in 2012; the wintering population rose 46% from 1998 to 2023, while monitored breeding numbers are similar to 1986 with falling productivity. The expansion has caused conflict with commercial fisheries and anglers, and the RSPB notes past persecution. In North America, Audubon's account (1996) describes a great increase and a breeding range spreading south into New England.