THE LONG-TAILED SKUA. 



'89 



tipped grey ; feathers of back and sides of neck with white bases 

 and brown subterminal patches and mostly with yellow pointed 

 tips ; rest of upper-parts black-brown, varying number of feathers 

 narrowly tipped white ; upper tail-coverts barred black and white ; 

 cheeks, ear-coverts and throat dull white speckled brown ; lower- 

 throat and breast brown ; flanks, under tail-coverts, axillaries and 

 under wing-coverts barred black and white ; centre of under -parts 

 white ; wing-coverts very narrowly edged whitish, lesser coverts 

 more broadly so. The juvenile plumage appears to be completely 

 moulted in early spring. 



Second summer. — Material is quite insufficient to make certain 

 of the sequence but apparently bird is like first summer but neck 

 and throat with more yellow and less brown, mantle more barred 

 with white, under-parts white and flanks less barred. 



Third summer. — A mixture of plumage partly like adult winter 

 and partly like adult summer but under wing-coverts and axillaries 

 always considerably barred or edged with white. It is probable 

 that some birds (judging by their tail-feathers) attain this plumage 

 in second summer. 



Fourth summer. — Like adult but with some barred or white- 

 tipped under wing-coverts or axillaries, and usually with one or 

 two winter-like barred or white-tipped upper or under tail-coverts. 



Measurements and structure. — $ wing 300-320 mm., tail : (ad.) 

 central 275-355, outer 160-250 shorter, (juv. both sexes) central 

 118-135, outer 25-30 shorter, (1st summer) central about 70 longer 

 than outer and tips tapering abruptly to long point, (3rd summer) 

 central about 100-130 longer than outer and tips more gradually 

 tapering, tarsus 35-44, bill from feathers 26-30 (15 adults measured). 

 $ wing 290-320, tail : (ad.) central 275-330, outer 160-220 shorter ; 

 bill 25-30. Primaries : 1st narrow and 

 about two - thirds primary - coverts, 2nd 

 longest, 3rd 10-20 mm. shorter, 4th 30-40 

 shorter, 5th 50-60 shorter. Tail as Arctic 

 Skua but central pair in adult tapering more 

 gradually to much prolonged point. Rest 

 of structure as Arctic Skua but bill not so 

 wide at base. Distance from feathers to 

 end of shield often from 1—4 mm. shorter 

 than from end of shield to tip of bill, 

 while in Arctic Skua distance is usually 

 same but often 1 mm. shorter or longer 

 and this distinction is not invariable. 



Soft parts. — Bill black ; legs and feet : 

 (ad.) tarsus slate-grey, tibia, joints, toes 

 and webs black, (juv.) only distal half of webs black ; iris dark 

 brown. 



Characters. — No subspecies. Smaller, narrower bill, very long 

 tail-feathers, greyer upper-parts are distinguishing characters (see 



Bills from above of— A. The 



Arctic Skua (S. parasiticus). 

 B. The Long-tailed Skua (S. 



longicaudus). 



