The Dominican Gull, which belongs to the same section of the group as the well-known Black-backed Gulls of Europe, is common throughout the Plata district in winter, from April to August. During the summer months it confines itself to the Atlantic coast, and breeds in large numbers in the neighbourhood of Bahia Blanca, on the extensive sand-banks and mud-flats there; and in other suitable localities further south. Durnford found it nesting at Tombo Point, sixty miles south of the Chupat river.
At the approach of cold weather the Dominican Gulls leave the sea-shore and wander inland and northward. At this season they are exclusively flesh-eaters, with a preference for fresh meat; and when the hide has been stripped from a dead cow or horse they begin to appear, vulture-like, announcing their approach with their usual long hoarse pelagic cries, and occasionally, as they circle about in the air, joining their voices in a laughter-like chorus of rapidly-repeated notes. Their winter movements are very irregular; in some seasons they are rare, and in others so abundant that they crowd out the Hooded Gulls and Carrion-Hawks from the carcass; I have seen as many as five to six hundred Dominicans massed round a dead cow.
[417.] LARUS MACULIPENNIS, Licht.
(SPOT-WINGED GULL.)
Larus maculipennis, Scl. et Salv. Nomencl. p. 148; Durnford, Ibis, 1877, p. 202 (Buenos Ayres), et 1878, p. 405 (Centr. Patagonia); White, P. Z. S. 1882, p. 628 (Buenos Ayres); Saunders, P. Z. S. 1878, p. 201; Withington, Ibis, 1888, p. 472 (Lomas de Zamora). Larus serranus, Burm. La-Plata Reise, ii. p. 519. Larus cirrhocephalus, Scl. et Salv. P. Z. S. 1868, p. 146 (Buenos Ayres); Hudson, P. Z. S. 1871, p. 4.
Description.—Head and nape brownish-black (in breeding-dress); tail and underparts white; mantle pale grey; primaries black or dark grey, tipped with white, and with large elongated white patches on the outer portions of first to fifth, followed by a subapical black bar (in L. glaucodes the lower portion is white): underwing pale grey; bill, legs, and feet blood-red: length 16·0-17·0 inches, wing 11·5.
Three outer primaries of adult Spot-Winged Gull.
(P. Z. S. 1878, p. 202.)
Hab. Southern Brazil, Uruguay, and La Plata.
This common Black-hooded Gull is found throughout the Argentine country, down to Chupat in Patagonia, and is exceedingly abundant on the pampas of Buenos Ayres, where it is simply called Gaviota. In the month of October they congregate in their breeding-places—extensive inland marshes, partially overgrown with rushes. The nests are formed of weeds and rushes, placed just above the water and near together, several hundreds being sometimes found within an area of less than one quarter of an acre. The eggs are four in number, large for the bird, obtusely pointed, of a pale clay-colour, thickly spotted at the big end and sparsely on the other parts with black.