BLACK TERN. 531 



thologists of the United States, in some of which it is 

 abundant. 



Adult males and females in summer have the bill black ; 

 the irides dark brown ; whole head and neck dark lead 

 grey ; back, wings, and tail uniform slate grey ; breast and 

 belly, like the head and neck, dark lead grey ; vent and 

 under tail-coverts white ; legs, toes, and their short mem- 

 branes dark reddish-brown ; the whole length of the bird 

 nine inches and three-quarters ; the tail less forked than 

 in some other species; the wing from the carpal joint 

 to the end of the first quill-feather eight inches and a 

 half. 



Adult birds in winter have the forehead, the space be- 

 tween the beak and the eye, the chin, and throat white, 

 and I have seen an adult female specimen that had as- 

 sumed this white colour before leaving this country in 

 autumn. The other parts as in summer. 



Young birds of the year have the bill brownish-black ; 

 forehead, chin, throat, and a collar round the neck white; 

 crown of the head and the nape greyish-black ; feathers of 

 the back and wing-coverts light slate grey, margined with 

 brown or white, or partly with both ; primaries dark slate 

 grey ; the first primary lead grey ; rump and upper tail- 

 coverts greyish-white ; tail-feathers slate grey ; breast, 

 belly, and all the under surface of the body and wings 

 white. Before leaving this country the plumage on the 

 upper surface of the body in the young bird loses the brown 

 colour, becoming of a more uniform slate grey, but clouded 

 with dark lead grey. This Tern having once assumed the 

 dark colour peculiar to the breast and belly in summer, 

 does not afterwards become white on those parts at any 

 age or season. 



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