100 BRITISH BIRDS. [vol. vii. 



and the slow development of the young, only a single 

 brood is reared during the season, though, of course, 

 a. second egg may be laid if the first is taken or destroyed. 

 The clutch invariably consists of one egg,* which is laid 

 as a rule from about the beginning of May, though some 

 birds do not lay tiU the middle of the month. Mr. 

 Oswin Lee, when visiting the Bass Rock on June 8th, 

 found only two young hatched out. This would make 

 the earhest date for eggs about April 26th, but occasionally 

 they are found much earlier, as the late E. T. Booth 

 saw a young bird already hatched on May 10th, 1867. 

 In this case the egg must have been laid at the end 

 of March, quite a month earlier than usual {Rough Notes, 

 Vol. III.). 



The breeding-places are not abandoned until September, 

 and in some cases are still occupied in early October. 

 Thus in the Annals of Scott. Nat. Hist., 1908, p. 198, it 

 is stated that young in down were still in the nests on 

 the Bass on October 8th, 1907 ; and Mr. W. Eagle Clarke 

 mentions that the breeding-ledges at St. Kilda were still 

 occupied on October 8th and 12th {Studies in Bird 

 Migration, II., p. 233), but E. T. Booth was imable 

 to discover a single nesthng on the Bass on October 

 7th, 1874. 



In the Faeroes, MuUer states that eggs may be found 

 from April 14th onward, and that the young are never 

 fledged before September 8th, but exceptionally the old 

 birds may be seen on the cUffs till October 14th. In the 

 colonies on the south-west of Iceland, the eggs are laid 

 in May and young may be met with from early Jul\ 

 onwards, while at Grimsey the eggs are rarely seen before 

 the end of May or early June, and Hantzsch could see 

 no young in the nests on July 10th. Here the young are 

 frequently not fuUy fledged till the end of September, 

 though in the south of Iceland they may be seen from the 

 end of August onwards. 



* E. T. Booth states that he has once or twice in a season seen two 

 eggs in a nest, but ascribes it to two pairs using the same nest, or the 

 eggs having been moved by visitors (Rough Notes, Vol. III.). 



