128 PROCEEDINGS OF THE 



assigned for its decrease in numbers there is, that rats have 

 managed to dislodge them. Tiiis can, however, hardly be the 

 case, because the places, in which doubtless. Black Guillemots bred 

 when there, seem to me to be inaccessible even to a rat. 



On other islands of the west coast, however, it is not so uncom- 

 mon. At one locality where I have taken their eggs, some twenty 

 pairs or more were breeding in a colony. At this place few of the 

 eggs were placed in crevices in the perpendicular face of the cliff, 

 but mostly at the bottom of deep cracks or fissures in the surface 

 of the island, never far removed from the sea. Some of 

 these fissures were from six to ten feet deep, and it was only by 

 using a stick with a ring at the end of it, and a piece of netting 

 attached, that I could get out the eggs. On this occasion I caught 

 three of the birds on the eggs. Two of these birds proved upon 

 dissection to be males, as was noted by Mr MacLeay of Inverness. 

 The bare breast-spots were equally visible in them as in the 

 females, and in one specimen there were two such spots. These 

 facts prove that both sexes share in the duties of incubation, as 

 Thomson has remarked in his " Birds of Ireland." 



One of these same three birds was curiously mottled with white 

 all over the lower breast and belly, being part of the winter 

 plumage not yet changed into the pure black of summer. Such 

 specimens are not common in summer, but Mr MacLeay informed 

 me that he has on several occasions received them for preservation. 



The number of eggs laid by this species seems to be almost 

 invariably two, but occasionally only one. I never found more 

 than two. Most of those obtained at the above place were far 

 advanced in incubation. It is somewhat singular, therefore, to 

 find that Mr Anderson states most strongly that in Labrador 

 Uria grylle invariably lays three eggs. No doubt this singular 

 disparity in numbers is caused by a greater or less supply of their 

 favourite food in different localities, and the fact tliat the Black 

 Guillemot is infinitely more abundant in the Arctic regions than 

 with us, goes to prove that food is there most plentiful. 



The Black Guillemot cannot be considered an abundant species 

 in the west of Sutherland; indeed, I know of only two or three 

 localities where it breeds, though doubtless there are others 

 between Scowrie and Cape Wrath. On the north coast they are 

 more abundant, though a correspondent writes that there are none 

 #> breeding near Armadale. 



