i86 



GULL GROUP 



readily distinguished from that bird by the pointed tips of the middle 

 tail-feathers. The species is remarkable as being what naturalists call 

 dimorphic, that is to say, it presents two distinct phases of colour, one 

 of which is uniformly sooty, while the other has light under-parts. 



In addition to the shape of the elongated middle tail-feathers, 

 Richardson's skua may be recognised at all seasons by the white 

 shafts of all the primary quills. The general colour of the dark 

 phase is uniformly sooty ; but in the light phase there is a band of 

 smoky grey on the fore part of the breast ; the throat and a collar 

 round the neck are white with a buff tinge ; and the rest of the under- 



AKCTIC SKUAS, I'AI.K AM) DAKK IMIASKS. 



parts white. in immature birds of the light phase the under-parts are 

 yellowish brown barred with umber ; but the chick is uniformly pale 

 chocolate. Seventeen inches is the length of the adult, exclusive of 

 the 3 inches occupied by the middle tail-feathers. The two phases 

 interbreed, so that birds of an intermediate type are not unfrequcntly 

 seen. 



The breeding-range of this species includes the Arctic and sub- 

 Arctic circumpolar regions, descending in the eastern hemisphere about 

 to latitude 55 , and embracing the Orkneys, Shetlands, and Hebrides, 

 and parts of Sutherland and Caithness on the Scottish mainland, which 

 form apparently the most southern localities for nesting. In winter 

 these birds may be met with over a very large portion of the globe, 

 inclusive of New Zealand, the Cape of Good Hope, and southern 



