WHITE-WINGED BLACK TERN. 259 



those of the Black Tern, and exhibit the same variations, ranging from 

 greyish buff to huffish brown in ground-colour, more or less heavily spotted 

 and blotched with reddish brown and dark blackish brown. The under- 

 lying markings are pale grey. The eggs vary in length from 1"4 to 

 1'34.< inch, and in breadth from 1*01 to '95 inch. They vary considerably 

 in shape, some specimens being almost as much pointed at the large as at 

 the small end. 



In its winter-quarters in South Africa the White-winged Black Tern is 

 described by Ay res and others as frequenting lakes and swamps and 

 avoiding the sea-coast. It is said to hawk for insects on the wing like a 

 Swallow ; but its flight is described as unsteady, slow, and heavy. 



The White-winged Black Tern is about the same size as the Black Tern, 

 but has slightly longer wings, and the fork of the tail is not quite so deep. 

 The adult in summer plumage differs principally from that of the Black 

 Tern in having the slate-grey on the wings shading into white on the 

 shoulder; in having the upper tail-coverts and tail, as well as the under tail- 

 coverts, white ; whilst the rest of the plumage, including the under wing- 

 coverts, is greenish black, shading into slate-grey on the innermost 

 secondaries. The soft parts greatly differ, the bill being dark red, and the 

 legs and feet scarlet, but the irides are dark hazel. After the autumn 

 moult the mantle becomes slate-grey, the head and neck become white, 

 marked with black on the nape^ and the whole of the underparts 

 except the under wing-coverts, which are suffused with grey, become 

 white. 



After the spring moult the young bird differs from the adult in having 

 the lesser wing-coverts, the upper tail-coverts, and tail suffused with grey ; 

 whilst birds of the year differ from adults in winter plumage in having the 

 wing-coverts, the innermost secondaries, and the tips of the tail-feathers 

 with white margins and dark-brown sub-margins. Bill, legs, and feet 

 broAvn. 



Young in first plumage differ frpm birds of the year in having the 

 feathers of the mantle, the scapulars, and the Aving-coverts a darker slate- 

 grey, with buff margins and brown sub-margins. 



Young in down are pale chestnut, the upper parts mottled with blackish 

 brown, and the underparts slightly darker on the throat. 



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