670 GREAT BLACK-HEADED GULL. 



Kul (a little to the east of Lake Balkash) on May 9th, and on the 

 Saisan-Nor early in June. Prjevalsky observed it in long. loo'^ E. 

 on the Koko-nor, an elevated lake in the mountain-range between 

 Mongolia and China ; and it is probably found throughout Tibet in 

 summer, as it passes over Gilgit on its way to India. There it 

 frequents the rivers, lakes and coasts, down to Ceylon and Burma, 

 during the cold season. It is unknown on the Amur or along the 

 sea-board of China, while Cassin's record from Japan is the result of 

 an erroneous identification. 



Details are scarce respecting the breeding-habits of this Gull, 

 though, through the Moravian colony at Sarepta on the Lower Volga, 

 numbers of its eggs have been received ; these, which are laid on the 

 bare sand, are 3 in number, and in colour stone-drab, boldly streaked 

 and blotched with umber and black : measurements 2*95 by 2 in. 

 The cry is described as a harsh and raven-like croak : the food 

 consists of fish, crustaceans, locusts, reptiles &:c. 



The adult in breeding-plumage has the head jet-black ; mantle of 

 a darker grey than in L. ridibundiis ; secondaries with broad white 

 tips, which form a conspicuous alar bar ; primaries chiefly white, 

 barred with black from the ist to the 5th and slightly on the 6th ; 

 tail and under-parts white ; bill orange-yellow, red at the angle and 

 zoned with black ; legs and feet greenish-yellow, the webs orange. 

 There is considerable variation in size, and females are often so 

 much smaller than males as to have given rise to the belief that 

 they belonged to a distinct species ; length of a male 26 in., wing 

 19 in. In winter the head is merely streaked with blackish. The 

 young bird is mottled with brown on the upper-parts, and the 

 primaries are dusky-brown. From young members of the Herring- 

 Gull group it may be distinguished by the white margins which 

 extend for a long way up the outer webs of the secondaries, as 

 wtW as by the uniformity in the dark band which crosses the 

 tail : this band being mottled and broken up in other species. 

 The nestling differs from that of almost all the Gulls in being of 

 an unspotted greyish-white above, and clearer white below. 



The Gulls with hoods have been separated from the rest under 

 various generic names. The least objectionable is Chroicocephahis 

 of Eyton, based upon " coloured hood, small size, and more naked 

 tibiae " ; but as the second qualification did not suit the above 

 gigantic species, Kaup (who was at least logical) created for it the 

 genus Ichthya'etus. No term can be more inadmissible than Xe/iia, 

 as it should only be applied to a Gull with a forked tail. 



