(2075) Thalasseus bergii velox.
THE RED SEA LARGE CRESTED TERN.
Sterna velox Cretzsch., Atlas Reise nord Afr., ii, tab. xiii, p. 21 (Red Sea). Sterna bergii. Blanf. & Oates, iii, p. 314.
Vernacular names. None recorded.
Description. - Breeding plumage. Upper part of head, from fore-crown to nape, including well-developed crest velvety-black ; forehead, hind-neck and edge of wing white; upper plumage grey, tinged ashy; primaries edged black on the outer webs, blackish on the inner webs with broad, white wedge-shaped patch on the outer feathers gradually lessening inwardly and disappearing on the innermost; secondaries white on the inner webs and tipped white ; outer tail-feathers with white lores and dark grey tips; rest of plumage white.
Colours of soft parts. Iris dark brown; bill lemon-yellow; legs and feet black, the soles yellowish.
Measurements. Wing 340 to 376 mm.: tail 165 to 205 mm.; tarsus about 34 to 35 mm.; culmen 60 to 71 mm.
In Winter the head is white, the feathers with broad black centres, increasing in size on the nape, whilst the crest-feathers are all black.
Young birds have the upper parts dull brownish-grey, edged brown on the inner webs and buffish on the outer webs.
Distribution. Red Sea and East African coast. One or two specimens from Sind seem to belong to this paler race aud have small bills. It is only possible to discriminate between these two races if authentic bleeding birds are examined.
Nidification. This fine Tern breeds in great numbers on many of the islands in the Red Sea, off the coast of the whole of Somaliland and probably a good deal farther South. The eggs, which number one to three, varying in the different colonies, are laid in depressions scratched in the sand by the parent birds without any kind of shelter from sun or rain. The breeding-season is from June to August and if the birds leave the eggs exposed to the sun for too long they are rendered infertile and, indeed, sometimes half-cooked. The eggs of this Tern and of the Lesser Crested Tern are probably the most beautiful of all seabirds* eggs, even exceeding in variety of colour and richness of tint the eggs of the Sandwich Tern. The ground-colour varies from pure white through pale cream, salmon, buff or pink to deep warm salmon and buff and even to rich brick-red. The markings are of two kinds: either large bold blotchings of red-brown, purple-brown or blackish-brown, in some being smaller and more speckly ; the second type has the same coloured marks in large scrolls and scriggly lines all over the egg. Intermediate forms occur but are rare and in fewer eggs still the markings form clouds and blurred blotches. Secondary markings are few or obsolete and are of grey and pale lavender. One hundred eggs average 62.1 x 43.0 mm.: maxima 66.3 x 44.5 and 63.5 x 45.1 mm.; minima 58.1 X 43.0 and 59.2 x 39.8 mm.
Habits. The Terns of this genus are essentially Sea-Terns and keep exclusively to the sea coast, feeding on small fish, mollusca and, it is said, water insects. Fish they take on the wing, dropping like an arrow into the sea and often wholly submerging themselves in their attempts to seise their prey. Like all the Terns which feed thus, they fly along with bill held straight down as they watch for their dinner ; for a moment or two they hover with widespread tail and beating wings and then with a demi-somersault plunge down to the water. Their cry is a hoarse and loud edition of that of the Common Tern, very much like that of the Sandwich Tern but still louder and of a deeper tone.
* Mathews, * Birds of Australia,' ii, p. 340 et seq. (Sept. 1012).