Double-crested cormorant

How it lives

A very adaptable bird, found on coasts, bays, lakes, rivers and reservoirs. It nests in colonies, in trees, on sea cliffs or on the ground on islands. Birds begin to breed at about three years old. A clutch is usually 3 to 4 eggs, sometimes 1 to 7, and incubation takes about 25 to 33 days. Its feathers are not fully waterproof, so after diving it stands with its wings held open to dry.

Where it goes

Most double-crested cormorants migrate, flying in flocks that often follow coastlines or rivers. Some stay all year, for example in Florida and on the Pacific coast. Birds that breed in the north spend the non-breeding season in places such as the Bahamas, Turks and Caicos, Hispaniola and the Cayman Islands. Single birds have turned up in Ireland, Portugal and the United Kingdom.

We only draw a journey on the map when scientists have tracked it or clearly documented it. For this animal we have not found one yet.

Populations

Least Concern worldwide (IUCN, 2018), and numbers are increasing. It declined until the 1920s, recovered into the 1950s, fell again in the 1960s because of pesticides, and has grown since DDT was banned in 1972. Population estimates in the sources I read differ, from about 630,000 to about 3.63 million birds, so treat any single number with care. In places where fish farmers see it as a competitor, authorities manage numbers by methods such as culling and egg treatment. The species is now placed in the genus Nannopterum (Nannopterum auritum).