314 BRITISH BIRDS. 



the rest, both in the colour of the ground and in the style of spotting. 

 Probably in the latter cases the odd egg has been laid by a different bird. 

 The eggs of the Black-headed Gull vary in ground-colour from pale bluish 

 green to greyish buff and brown, spotted, blotched, and streaked, in almost 

 every conceivable variety, with surface-markings of dark brown and with 

 underlying markings of greyish brown. On some eggs the spots are much 

 darker than on others, and occasionally, but apparently only where the 

 ground-colour is pale bluish green, they are absent or nearly so. They 

 differ greatly in shape and size, varying from 2'45 to T95 inch in length, 

 and from T55 to T35 inch in breadth. The eggs of the Black-headed 

 Gull are indistinguishable from those of the Laughing Gull. Both male 

 and female assist in the duties of incubation, and but one brood appears to 

 be reared in the year. 



In winter the Black-headed Gull is a coast-bird, and frequents estuaries, 

 low-lying shores, and lagoons ; but it sometimes wanders inland at this 

 season, for Capt. Shelley observed it far up the Nile in large flocks, following 

 and preying upon a swarm of locusts. In India it frequents the large 

 rivers and inland lakes as well as the coast. It is as gregarious as in the 

 breeding-season, and large flocks often follow the shoals of fish for days. 

 The food of the Black-headed Gull is composed of insects of various kinds, 

 worms, small fish, crustaceans, &c. It feeds as greedily on wire-worms as 

 the Rook, and is very useful to the farmer in ridding the land of many 

 insect pests. 



The Black-headed Gull in full breeding-plumage has a sooty-brown 

 hood, which extends to the throat, but not to the nape; the mantle, scapu- 

 lars, wing-coverts, and innermost secondaries are French grey ; the pri- 

 maries are white, tipped with black, and the longest more or less margined 

 with black ; the rest of the plumage (including a ring round the eye) is 

 pure white, frequently suffused with rose-colour on the breast. Bill, 

 orbits, legs, and feet blood-red ; irides hazel. This plumage is acquired in 

 March ; the brown head is assumed in a fortnight, by a change of colour 

 and not by a moult, and it is not known that any of the other feathers are 

 moulted. The bird probably breeds when it is nearly two years old, but 

 the amount of white on the primaries increases at each successive autumn 

 moult for several years afterwards. After the autumn moult, which takes 

 place in August, and probably extends to every feather, the brown hood 

 disappears, except a patch on the lores and another on the ear-coverts, and 

 there are occasionally a few streaks on the hind head. After the first 

 spring moult, which is possibly confined to the scapulars and innermost 

 secondaries, the brown hood is more or less mottled with white, and 

 further signs of immaturity are to be found in brown streaks on the wing- 

 coverts, the greater amount of brown on the primaries, and in a more or 

 less imperfect brown band at the end of the tail. Birds of the year (a 



