Birds of Britain 



upper parts are pale slaty blue, the head and nape dusky 

 grey, chin and throat white. This plumage is, however, worn 

 for an exceedingly short time and is rarely complete, signs of 

 the new breeding dress appearing before all old feathers 

 have been cast. 



The winter feathers of the head and neck are downy. 

 Length 30-32 in.; wing 1314 in. 



THE WHITE-BILLED NORTHERN 

 DIVER 



Colymbus adamsi, Q. R. Grey 



This species breeds in the Far North, wandering south in 

 winter ; two or three examples have been taken on our 

 shores, and it is probable that owing to its resemblance to 

 the preceding species it has been often overlooked. 



The chief characteristic is the bill, which is yellowish 

 white at all seasons, and the lower mandible is also 

 markedly upturned. The white streaks on the transverse 

 throat bands are much fewer in number than in the 

 preceding species. Length about 33 in.; wing 15"1 in. 



THE BLACK-THROATED DIVER 



Colymbus arcticus, Llnnreus 



The Black-throated Diver is very rare in England, and 

 the few examples that are obtained are usually immature. 



384 



