(2085) Sterna hirundo longipennis.
Sterna longipennis Nordmann, in Erman's Reise, p. 17 (1835) (Ochotok); Blanf. & Oates, iv, p. 319.
Vernacular names. None recorded.
Description. About the same in colour as the Tibetan Tern but always distinguishable in breeding plumage by its wholly black bill and feet. It is rather darker both above and below than the Common Tern, whilst it is decidedly smaller with a smaller bill.
Colours of soft parts. Iris brown ; bill and feet black.
Measurements. Wing 230 to 272 mm.; tail 110 to 130 mm.; tarsus 19 to 21 mm.; culmen 29 to 35 mm.
Birds in Winter plumage and young birds resemble the preceding subspecies except for their black feet and bill.
Distribution. From Lake Baikal to the extreme East of Siberia and Japan and along the Chinese coast. In Winter it wanders South and West into South China, the coasts of the Indo-Chinese countries and once as far as Ceylon.
Nidification. Owston's collectors found breeding colonies of this Tern in Sakhalin on the coast. They were breeding just above high water on the line of the extreme tide, the eggs being laid in the rubbish thus formed. Each nest contained three eggs which can be exactly matched by many of the Common Tern. The ground-colour is pale yellowish-stone, pale olive, rather dark olive-green or light brown and they are all well blotched with dark reddish-brown and secondary blotches of neutral tint, more numerous at the larger end. The average of twenty-five eggs is 42.7 x 30.0 mm.: maxima 46.0 X 31.4 and 43.0 x 32.5 mm.; minima 38.3 X 28.6 mm. Owston took all his eggs in June but in Kamtschatka eggs were obtained on the 4th of May.
Habits. Much the same as those of the Common Tern. This Tern frequents both the larger inland lakes and marshes and the sea coast, feeding entirely on fish and aquatic insects and keeping in flocks at all times.