WHITE-BILLED NORTHERN DIVER. 303 



The spring moult begins in December, but full dress may 

 not be attained until May. The head and neck are then 

 black, glossed with purple and green ; under the chin and on 

 the sides of the neck are bands of white streaked with black, 

 and below the black on the sides of the white breast are wavy 

 slate-grey lines. The upper parts are glossy black, plentifully 

 spotted with white ; on the mantle the spots are large and 

 square, arranged in regular bands. The quills and tail are 

 black. The bill is blue-black, the legs have a greenish tinge, 

 and the irides are crimson. A bird in early January with the 

 throat still white, had the back black with ordered rows ol 

 spots. In winter the only indication of the throat adornment is 

 a dark patch on the side of the neck ; the head and nape are 

 sooty, and the upper parts ashy grey with obscure spots, giving 

 a mottled appearance. The tail is tipped with white. The 

 bill is bluish horn, much lighter than in summer, and the 

 irides are reddish. Young birds have the crown and nape 

 grey, the face suffused with brown, and the feathers of the 

 upper parts show pale edges, often as regular but indistinct bars. 

 The irides were brown in a bird I examined. Length, 31 ins. 

 Wing, 14 ins. Tarsus, 3*6 ins. 

 • 



White-billed Northern Diver. Colymbns adamsi Gray. 



The White-billed Northern Diver breeds in the Arctic from 

 Novaya Zemlya eastward to Alaska, and about half a dozen 

 have been obtained in Great Britain, though it is possible that 

 it has often been overlooked. Seebohm's supposed differences 

 between this bird and the Great Northern in summer plumage 

 are not sound ; the green and purple gloss on the head and neck 

 varies individually, and certainly in the latter species the number 

 of the streaks on the neck bands is not constant. This bird is, 

 however, larger, and has a deeper and more massive bill, 

 which at all seasons is yellowish white ; the colour alone is not 



