Great Northern Diver

The great northern diver (Gavia immer) is a visitor to British coasts and only breeds rarely here. It can be seen from October to May around Scotland, Ireland, the Isle of Man, north and west Wales and south-west England.

The great northern diver breeds in North America (where it is known as the common loon), Iceland and Greenland.

Appearance

The great northern diver measures 30-33 inches (76-84 cms) in length.

It is notable for its large, bulky form and heavy dark bill. The upper plumage (in summer) is dark with prominent white spots. The head and neck are almost black (with a greenish sheen) with black and white striped patches. The underparts are brilliant white, being apparent when the bird rolls in the water to preen itself.

The winter plumage is much duller and less impressive, without the spots and patches.

The sexes look alike in all respects.

Behaviour 

The great northern diver is most at home on the water, where it feeds, being ungainly on land. It swims low in the water and dives smoothly and powerfully. It can dive for a minute or more at a time. If alarmed it will swim with only its head and neck above the surface.

Food is mainly fish, particularly haddock, herring and sand-eels, but it will also take crustaceans such as crabs, and insects.

It is a strong flyer, despite its small wings, and it can only take off from the water with considerable effort. The wingbeats are slower than those of other divers and its silhouette is goose-like, with a drooping neck.

Call

The great northern diver is renowned for its eerie call, consisting of moans and howls that have often featured on film soundtracks when a director wants to heighten tension in a scene that depicts something frightening or supernatural. However, these calls are merely territorial claims on the part of breeding birds. The birds are virtually silent at other times.

Breeding

Two eggs are usually laid in a nest made from vegetation near the water’s edge. When hatched, the young birds will ride on their parents’ backs. They will breed themselves after they are two years old.

© John Welford