198 BRITISH BIRDS. 



Sub-Family Stercorariinee 



GENUS CXC1I. STERCORARIUS, Brisson (/760). 



Bill strong, tip of upper mandible dilated, decurved and 

 somewhat hooked. Nostrils placed toward extremity of 

 bill, narrow and oblique. Toes with large hooked claws. 



351. Stereorarius eatarrhaetes (Linn.)- COMMON 

 SKUA. 



Hab. N.W. Europe and Eastern Arctic America. 



Adult : feathers above and below chiefly dark brown 

 with rufous margins ; primaries white on basal portion ; 

 bill and feet blackish. Length about 22*00 ; wing i6'oo. 



Small protected colonies exist in the Shetlands, but it 

 does not breed elsewhere, neither is it very plentiful on our 

 coasts in winter ; it is rarely recorded from Ireland. 



352. Stereorarius pomatorhinus (Temm.). 



POMATORHINE SKUA. 



Hab. Arctic regions of Asia and America. 



An irregular visitor in autumn and winter, occurring 

 annually in vaiying numbers on the east side, but more 

 rarely on the west and in Ireland. It is larger than the 

 next species, and the adult has the two elongated middle 

 tail-feathers broad and twisted into a vertical position. 



353. Stereorarius erepidatus (Gmel.). RICHARD- 

 SON'S SKUA. 



Hab. Northern Palaearctic and Neferctic regions. 



There is a light and a dark phase of this Skua, extremes 

 of former having throat and breast white, and extremes of 

 latter having whole plumage dusky brown, but the two 

 constantly interbreed, and every intermediate stage is to 

 be found. In adults two middle tail-feathers are elongated 



