58 



LARIDJE. 



Arctic. 



Arctic. 



343. ICELAND GULL. Larus leucopterus, Faber. Winter straggler. 



Like last, but smaller ; wings relatively much longer, being nearly 

 as long as those of last. 



Young. As in Glaucous Gull. Length 22 inches. 



344. KITTIWAKE. 

 Nests on rocks. 



Rissa tridactyla (Linnaeus). Partially resident. 



Hind toe absent or rudimentary. 



In summer. Head, neck, and tail pure white ; bill greenish yellow. 

 In winter. Head and neck slate-grey. 



Young. Bill black ; brown feathers on back ; tail with black band at 

 end. Length 15 inches. 



345. IVORY GULL. Pagophila eburnea (Phipps). Rare, in winter. 



Entirely white ; legs black ; tail rather long and slightly graduated ; 

 hind toe connected with leg by a web. 



Young. Black spots on wings, tips of quills, and tail-feathers ; still 

 younger birds have black spots also on back. Length 16-18 inches. 



Sub-arctic. 





Arctic, to 



N. Australia in 



winter. 



\fl 



82 N., to 



N. Zealand in' 



winter. 



Subfamily STEECOBABIIN^. BOBBER-GULLS. 



Base of upper mandible covered with a cere or skin, and hooked at 

 the point. 



346. GREAT SKUA. Stercorarius catarrliactes (Linnaeus). Breeds in 

 Shetlands, where it is now protected. 



General colour above dark brown ; below lighter brown ; axillaries 

 dark brown ; primaries blackish brown, bases white, forming a well- 

 marked band. Tail dark brown, white at the base, but this is hidden by 

 the coverts ; two centre feathers very slightly longer than the others. 

 Length 24-25 inches, leg 2J-3 j. 



347. TWIST-TAILED or POMATORHIFE SKUA. Stercorarius pomato- 

 rhinus (Temminck). Autumn to spring. 



Two forms or races are found, both dark brown above. The dark 

 form as dark below as above ; the light form white below, barred on 

 flanks and tail-coverts with dark brown, white on the throat, tinged 

 with golden yellow, and sometimes extending round nape. 



Centre tail-feathers *4 inches longer than the others, and twisted 

 upwards. 



Young. Above dark brown ; below paler, with buff margins to the 

 feathers ; tail brown, two centre feathers only very slightly longer than 

 the others. Length 21 inches, leg 2. 



348. BIOHARDSOX'S SKUA. Stercorarius crepidatus (J. F. Gmelin). 

 Breeds on one or two places on the mainland and on some of the islands 

 of N. of Scotland. 



Two forms or races are found. 



