(2083) Sterna hirundo hirundo.
THE COMMON TERN.
Sterna hirundo Linn., Syst. Nat., 10th ed., i, p. 137 (1758) (Sweden). Sterna fluviatilis. Blanf. & Oates, iv, p. 318 (part.).
Vernacular names. None recorded.
Description. Whole crown black to nape and end of crest; back and wings grey ; the greater coverts tipped white; first primary blackish, the inner web broadly edged with white; second more grey with the edge of the inner web near the tip brownish-black, the succeeding feathers more grey with less white on the inner webs; rump and upper tail-coverts white; tail white, the outer webs of the outermost feathers blackish and of the others grey ; lower plumage white, suffused with vinous-grey from the breast to the vent.
Colours of soft parts. Iris dark brown ; bill coral-red, broadly tipped with blackish; legs and feet coral-red
Measurements. Wing 254 to 286 mm.; tail 130 to 172 mm.; tarsus about 20 to 21 mm.; culmen 35 to 39 mm.
In Winter the forehead, fore-crown and upper lores are white streaked more or less with black, especially on the nape, which is often wholly black; lower parts white. The bill is duller and blackish and the feet also duller red.
Young birds have the upper parts buff barred with dark brown and the feathers margined paler; the forehead and fore-crown is brownish-buff, the hind-crown streaked with black and the nape all blackish; the lower plumage white ; bill blackish, feet blackish-red.
Nestling in down. Above pale sandy or buff, the crown marked with black, generally, in two fairly well-denned lateral bands and a less well-defined central one ; back mottled with black; throat and fore-neck purplish-brown, paler on the chin, rest of down on under parts white.
Distribution. Temperate Europe and Asia, extending South in Winter to North-West India and Northern Africa. Within our limits it occurs on the Mekran and Sind coasts and probably most of the Terns of this species wintering on the West coast of India are of this race, whilst those found inland and Eastwards are of the Tibetan race.
Nidification. The Common Tern breeds in Mesopotamia but not nearer than this to India. In most countries it is a shore-breeder but in Mesopotamia and West Central Asia it breeds on the shores of the great lakes and swamps. The nest is a scratching in the sand or mud,sometimes entirely unlined, sometimes with quite a good nest of grass etc. The eggs number two or three and vary very greatly in colour. Normally the ground may be pale stone, pale greenish, pale olive-, buff or yellow-brown and range from this to deep tints of the same, speckled, spotted or blotched with various shades of red-browns and browns. Exceptional eggs may be of almost any colour, from unspotted pale blue to pink blotched with blood-red. One hundred British eggs average 41.2 x 30.3 mm.
The breeding-season is from the last few days of April to the end of June, the vast majority of English birds laving between the 25th of May and the 10th of June.
Habits. A very sociable bird, being found in large flocks throughout the year, living almost entirely on fish, sand-eels and aquatic insects, which it obtains by diving from a height into the water.