352 BIRDS OF TUNISIA 



also frequently to be met with in pairs. It frequents the sea-coast, 

 as a rule, or salt-water lagoons not far from the sea. Its flight, 

 though rather heavier than that of most Terns, is powerful and 

 untiring, the bird, like others of its kind, spending its life chiefly in 

 the air. Like them too, when scanning the water in search of food 

 it carries its bill pointing downwards, almost at a right angle to 

 its body. It lives principally on fish, but is said also to prey on the 

 eggs and young of other sea-birds. 



Its note is a harsh "quad, quad." 



When its breeding- grounds are approached, the bird becomes very 

 noisy, and will boldly come within easy gunshot of the intruder, 

 crying out lustily. 



It breeds in communities and in isolated pairs, generally on small 

 unpopulated islands, where it is less likely to be disturbed. Its eggs, 

 two or three in number, and placed in a slight depression in the bare 

 ground, occasionally surrounded with a few shells, or pieces of sea- 

 weed, are buff-colour, sometimes }'ellower, at others greener or whiter, 

 rather sparingly marked with underlying pale grey blotches and brown 

 surface-spots. The markings are generally distributed over the 

 whole surface, but occasionally collected at the larger end of the egg. 

 Average measurements 63 x 45 mm. 



STERNA MEDIA, Horsfield. 

 ALLIED TERN. 



Sterna media, Horsf. Trans. Linn. Soc. xiii, p. 199 (1820) ; Eocnig, 

 J. f. 0. 1893, p. 97 ; Saunders, Cat. Birds Brit. Mas. xxv, p. 86. 



Sterna aflBnis, Malherhe, Faune Orn. de I'Alg. p. 34 (1855). 



Thalasseus afflnis, Lochc, Expl. Sci. Alg. Ois. ii, p. 200 (1867) ; Eocnig, 

 J.f. 0. 1888, p. 284. 



Description. — Adult male, summer, from Djerba, South Tunisia. 



Forehead, crown and nape jet black ; neck and mantle white ; remainder 

 of the upper plumage pearl-grey ; primaries with dark grey stripes on their 

 inner webs, adjoining the shafts, which are white ; entire underparts white. 



Iris dark brown ; bill yellow ; feet black. 



Total length 15 inches, wing 11-50, culmen 2-50, tarsus I'lO. 



Adult female similar to the male. 



