850 



ALCAD.E. 



tliis species in its summer-plumage. The beak is black, its 

 shape has been referred to, the posterior half of the marginal 

 portion of the upper mandible nearly white, extending from 

 the corner of the mouth to the point Avhere the feathers pro- 

 ject on the bill ; the irides dark ; head, throat, neck behind, 

 back, wings, and tail sooty black ; secondaries tipped with 

 white ; belly, and all beneath pure white, running up to a 

 point on the front of the neck ; in the Common Guillemot 

 the white colour ends here in the form of a rounded arch ; 

 legs, toes, and their membranes brownish-black. The whole 

 length eighteen inches. From the wrist to the end of the 

 longest quill-feather eight inches and a quarter. The sexes 

 are alike in plumage. 



This species undergoes the same changes of plumage from 

 season as the U. troile. Colonel Sabine remarks that speci- 

 mens killed early in June had the throat and neck white, 

 unmixed with black ; towards the end of June the change 

 was in progress, and by the second week in July, as many 

 were found in perfect summer-plumage, with black throats 

 and necks, as were still in change. M. Temminck says the 

 young assume, in March, their first summer-plumage. Adult 

 birds lose their black throat at the autumn moult. 



