British Sea Birds

by Charles Dixon

GREAT NORTHERN DIVER.

This species, the Colymbus glacialis of Linnæus and of ornithologists generally, is, in its breeding plumage, one of the handsomest of British birds. Its chief characteristics are its large size—about that of a Goose—black head and neck, double semi-collars of white and black vertical stripes, and black upper parts, marked with white spots of varying size, and arranged in a series of belts. Whether it actually breeds within our limits has not yet been absolutely determined, although evidence is forthcoming that seems to point to the fact. Unfortunately for the seaside student of bird life, the Great Northern Diver is only known as a winter visitor. At that season, however, it may be met with pretty frequently off the British coasts, the young birds especially venturing into our bays and creeks and estuaries, older individuals, as a rule, keeping further out to sea. Adult birds are, however, often observed near the coasts of South Devonshire and Cornwall. I have known them linger in the waters near here until the summer has been well advanced. Young birds of this species, in the brown and white dress characteristic of immaturity, may often be seen quietly fishing under the cliffs, notably in Tor Bay. One very remarkable thing about this Diver is its singular habit of immersing the body to such a depth that the back is quite under water. It often so sinks itself when menaced by danger, and then, almost out of sight, swims away with great speed. If pursuit is still continued all but the neck is sunk below the surface, and finally, if hotly pressed, the bird will disappear entirely, and swim along under water at a speed absolutely astonishing, Gätke records that this Diver, when chased by a boat under these circumstances, will dive and allow the boat to pass over it, rising again in the rear of it, a habit which my own observations of the bird completely confirm. How this act of immersion, without apparent effort, is accomplished remains a mystery, and offers a problem in animal mechanics by no means easy of solution.

The Great Northern Diver is rarely seen on land, perhaps never except during the breeding season. Its movements on shore are ungainly in the extreme, the legs being placed so far back that the bird can only push itself along in a crawling sort of a way; it is equally rarely seen in the air, and apparently only uses its wings to fly when performing its annual migrations. How the species still retains the function of flight at all seems almost a mystery, but perhaps the constant use of the wings in the water keeps them to a standard of efficiency. This Diver is one of the least gregarious, and save on passage is rarely met with in numbers greater than a pair. It seems to be the rule for odd pairs to take up their residence in certain spots during the breeding season; after that period the bird is usually met with solitary, and the young individuals, unlike so many others that evince strong gregarious propensities, for the most part wander about alone. This Diver, like most big birds, is shy and wary, although I have repeatedly watched it from the cliffs in Tor Bay evincing little concern at my presence. As may be gathered from the foregoing remarks the Great Northern Diver is a proficient in the art of diving, and is said to be able to remain as long as eight minutes beneath the surface—a period of time which seems incredible. The depth to which it sometimes descends is also enormous—it has been captured in a net thirty fathoms from the surface. The food of this Diver is almost, if not absolutely, composed of fish. During the non-breeding season Divers are not particularly noisy birds, but at their nesting-places the cries they utter are both loud and startling, described by some listeners as similar to the screams of tortured children; as shrieks of maddened laughter, or as weird and melancholy howls by others.

It is a somewhat remarkable fact that the Great Northern Diver breeds nowhere in Europe, except on Iceland. It is an American species, and nests from Greenland westwards to Alaska, south of the Arctic circle to the more northern of the United States. It reaches its breeding-grounds in pairs towards the end of May, as soon as the northern waters are free from ice. Its favourite nesting places are secluded tarns and lakes, and an island is always selected if possible, doubtless from motives of security. The nest—always made upon the ground—varies a good deal in size, according to the local requirements. On wet marshy ground it is large, and composed of a heap of half rotten sedges, rushes, reeds, and such like vegetation, lined with dry bits of broken reed and withered grass. On drier and barer situations it is little more than a hollow in the sand or hard ground, with, perhaps, a few bits of dry grass for lining. The birds are very alert and watchful whilst nesting, as if fully conscious of their comparative difficulty in escaping from danger on the land. One bird is generally on the look out whilst the other sits, and at the least danger the alarm is given, and the incubating partner shuffles off in a floundering way to the water. A path is soon thus worn from the nest to the lake. The eggs are almost invariably two, elongated, and varying in ground colour from russet-brown to olive-brown, spotted sparingly with blackish-brown and paler brown. When the young are sufficiently matured, the inland haunts are deserted, and the nomad wandering life upon the sea resumed.