ARCTIC TERN. 557 



momentarily hides them from the view of any one nearly on 

 the same level, but when watched from a commanding posi- 

 tion the Editor has never witnessed complete submergence, 

 and certainly no approach to diving. 



The adult bird in summer has the bill coral-red ; iris dark 

 brown ; forehead, crown, and nape black ; back, wings, and 

 wing-coverts pearl-grey ; outer web of the first primary lead- 

 grey ; tail-coverts and tail-feathers white, the two longest 

 tail-feathers on each side grey on the outer webs ; chin and 

 cheeks white ; upper part of neck in front and on the sides, 

 ash-grey ; breast and all the under surface of the body as 

 dark a grey colour as that of the back ; legs, toes, and their 

 membranes orange-red. The whole length of the bird, from 

 the point of the bill to the end of the middle, or short, tail- 

 feather, is twelve inches and a half, to the end of the longest 

 tail-feather two inches and a half more, or fifteen inches 

 whole length ; from the wrist to the end of the longest quill- 

 feather, eleven inches; length of the tarsus only half an inch. 



A young bird of the first autumn, nearly full-grown, and 

 measuring thirteen inches, has the bill dull brown at the 

 point, the remainder red ; forehead dull white ; crown of the 

 head mottled black and white ; back of the head and nape 

 uniform dusky-black ; back and wings pearl-grey ; outer web 

 of the first primary lead-grey; inner webs of all the primaries 

 light grey, almost white ; secondaries, tertials, scapulars, 

 and small wing-coverts tipped with white ; upper tail-coverts 

 and tail-feathers white, the three long tail-feathers on each 

 side with outer webs of slate-grey; throat, breast, and all 

 the under surface of the body and wings at this age nearly 

 pure white ; legs, toes, and membranes orange. Up to 

 October all the upper parts are more or less barred with 

 brownish- grey, which wears off with increasing age, and by the 

 following July, just previous to the moult, the black bill, the 

 white forehead, the dark bar on the carpals, and the shorter 

 tail-streamers are almost the only signs of immaturity. 



The downy nestling when a few days old is rather less 

 buff and more greyish than the Common Tern, and there is 

 less black on the throat : otherwise there is little difference. 



