676 LARID^. 



which was so remarkable for the visitation of the Pomator- 

 hine Skua, and Mr. T. H. Nelson informs the Editor that, on 

 the 12th July, 1881, he observed a flock of about 100 going 

 north-west : an occurrence remarkable both as regards date 

 and direction of flight. A few birds which are not breeding 

 may from time to time be observed during the summer. On 

 the south coast of England this species is less abundant, 

 and to Cornwall its visits appear to be decidedly rare, nor is 

 it of regular occurrence on the western side of our island. 

 Stragglers, chiefly birds of the year, have been shot in several 

 of our inland counties, generally in the vicinity of rivers or 

 sheets of water. On the spring migration it is far less 

 numerous than in autumn. 



It is now well known that the Arctic Skua occurs under 

 two very distinct plumages, even in the same breeding-places : 

 one form being entirely sooty, and the other having light 

 underparts. The white-breasted birds pair with whole-coloured 

 birds as well as with those of their own variety, the dark- 

 coloured birds also pairing together. Both the extreme 

 forms, and the gradations resulting from their union, are 

 found breeding on our northern islands, the Faeroes, Iceland, 

 the coasts of Norway, Sweden, Siberia, and, probably, on 

 Novaya Zemlya ; but on Spitsbergen neither Dr. Malmgren 

 nor Prof. Newton observed a single specimen of the dark 

 whole-coloured form, and all those which Admiral Collinson's 

 and Dr. Rae's expeditions brought home from the far north 

 of Arctic America were white-breasted birds, which looks as 

 if the dark variety might be a more exclusively sub-arctic 

 one. At all events, it seems tolerably well proved that 

 whereas towards the southern limit of its breeding- range 

 the dark form predominates, the white-breasted variety in- 

 creases in proportion to the northwards, until it attains the 

 ascendency. In America, below the Arctic Circle, both forms 

 are met with, and it was, in fact, in the Hudson's Bay Terri- 

 tory that the dark specimen was obtained on which Swainson 

 bestowed the name of Lestris richardsonii, in compliment 

 to Sir John Richardson. As a breeding species the Arctic 

 Skua may be broadly described as sub-arctic and circumpolar; 



