670° GREAT BLACK-HEADED GULL. 
Kul (a little to the east of Lake Balkash) on May oth, and on the 
Saisan-Nor early in June. Prjevalsky observed it in long. 100° 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 ZL. rtdibundus ; secondaries with broad white 
tips, which form a conspicuous alar bar; primaries chiefly white, 
barred with black from the rst 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 
well 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 Chvoicocephalus 
of Eyton, based upon “ coloured hood, small size, and more naked 
tibie ”; but as the second qualification did not suit the above 
gigantic species, Kaup (who was at least logical) created for it the 
genus Jchthyaétus. No term can be more inadmissible than Xema, 
as it should only be applied to a Gull with a forked tail. 
