460 ALCAD^E. 



bine's description of this 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 man- 

 dible nearly white, extending from the corner of the mouth 

 to the point where the feathers project 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 

 is 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 

 specimens 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. 



