56 Proceedings of the Royal Physical Society. 



we are both persuaded that they do so on the western cliffs 

 of Priest Island, which we were unable to visit. 



33. Uria grylle (Linn.). 



(Black Guillemot.) 



Very common, and found nesting in more or less abund- 

 ance on Priest Island, Tanera Beg, Eilean Dubh, Glasleac 

 Mor, Bottle Island, and Carn Deas. This bird is stated by 

 all authorities whom I have consulted to deposit its eggs 

 on the bare ground; and Saxby affirms that though he 

 has found them 50 or 60 yards inland, on grassy slopes 

 strewn with rocks, he never found them in anything like 

 a nest. On the other hand, Mr Bonar never, in one single 

 instance, out of the many found by him, observed the eggs 

 of this species deposited on the bare ground. Without 

 exception the eggs were resting on small gravel, which had 

 probably been carried thither by the bird. In one instance, 

 fragments of bones bleached by the rain were used, along with 

 the gravel, to form the receptacle for the eggs. He was so 

 greatly impressed with this interesting discovery, that he 

 took particular care to examine every nesting-site of this 

 bird which came under his observation. One of our ghillies 

 climbed to a nest on Glasleac Mor, and reported that the 

 eggs were placed on the bare rock ; but, having been asked 

 to look more carefully, he ascertained that the bird had laid 

 on a layer of small pebbles. We are, moreover, of opinion 

 that the gravel is carefully selected by the parent birds, for 

 round and round the eggs it was all of one size — indeed, it 

 may be described as being just the size of that employed by 

 the Oyster-Catcher for lining the hollow of its nest. Further- 

 more, in several cases a slight hollow had been made by the 

 sitting bird. 



Mr Bonar, on 18th June, found on Glasleac Mor a nest 

 of the Black Guillemot which contained three eggs; but 

 it by no means follows that they are the produce of one 

 and the same bird — indeed, I am strongly of opinion that 

 they are not. 



