The Black Tern — Hydrochelidon Nigra (Linnæus)
Up till the middle of last century the Black Tern was a regular summer visitor to our shores, remaining to breed in the fens and marshes of England. For the last forty years, however, it has only occurred on passage, the adult birds passing through in April and May, and flocks in immature plumage being found along the east coast in the autumn. To the west of England and Scotland it is a very irregular visitor, and the same may be said of Ireland.
It nests in colonies on inland marshes, the nest being an accumulation of decaying vegetation floating on the surface of the water. The eggs, three in number, are olive green blotched with dark brown. Its food consists largely of aquatic insects and their larvæ, dragon-flies and such like, but it also feeds readily on small fish.
South of the Baltic it breeds in suitable localities throughout Europe, migrating from its more northerly summer quarters to Africa.
The adult in summer has the head, neck, and under parts dark greyish black, the rest of the plumage slate grey, except the vent and under tail coverts, which are white. Bill black. In winter the forehead, nape, chin, throat, and under parts are white. The young resemble the adults in winter, but the upper tail coverts are lighter and the back and wing coverts are greyish mottled with brown. Length 10 in.; wing 8·5 in.