GULL-BILI.ED TERN. 
Ill 
The adult bird measures thirteen inches and a half in 
length ; the beak one inch and a half from the forehead ; 
the tarsus one inch three lines ; the wing nearly fourteen 
inches ; the outer tail-feathers five inches; the middle tail- 
feathers four inches, three to four lines. In summer the beak 
is black, and six lines deep at its base, and the angle on 
the lower mandible by far more abrupt than in that of the 
terns in general. The iris is dark brown; the legs and feet 
are reddish black. The forehead, crown, and nape are black; 
the feathers silky and rather elongated; on the top of the 
head there are always a few feathers with white edges. The 
upper plumage is pale bluish gull-grey ; the quill-feathers are 
blackish or hoary grey, the tips of the first five feathers are 
black; the chin, throat, neck, breast, and all the under parts 
are white. The claws of this bird are very long and straight. 
The winter plumage has the forehead and crown white ; a 
spot before the eye, and behind the ear-coverts of greyish 
black ; the rest of the plumage as in summer, but the black 
tips of the quill-feathers are not so deeply coloured. 
