THE ARCTIC SKUA. 78o 



mottled or barred black-brown, lower flanks and under tail-coverts 

 usually more prominently barred or tipped buff or rufous ; sides of 

 head, chin and throat, in examples with lighter under -parts, usually 

 streaked black-brown but occasionally uniform black-brown ; 

 axillaries and under wing-coverts black-brown tipped rufous or 

 buff and in lighter examples broadly barred brown and buff or 

 whitish ; tail brown-black, concealed base white often tinged 

 rufous, outer feathers with very narrow tips or spots at tips of buff ; 

 primaries as adult but with conspicuous rufous or buff tips and 

 white at base of outer primaries often showing (usually tinged 

 rufous) beyond primary-coverts ; secondaries brown-black, inner- 

 most usually but not always tipped rufous or buff ; primary-coverts 

 brown-black tipped rufous but often very lightly ; greater coverts 

 black-brown usually edged and tipped rufous or buff but occasionally 

 uniform ; median and lesser coverts as upper -parts but upper series 

 of lesser broadly edged and tipped rufous-buff to buff. N.B. — Buff 

 or rufous tips to feathers become much worn in winter. 



First summer. — Much as juvenile but crown rather darker ; 

 back of neck usually barred ; many feathers of mantle and scapulars 

 tipped rufous or buff but some not ; tail-coverts, axillaries and 

 under wing-coverts boldly barred ; under-parts barred varying in 

 colour ; primaries and primary-coverts as adults without buff tips ; 

 wing-coverts tipped buff. The juvenile plumage is completely 

 moulted (including wings and tail) Nov. to March, and occasionally 

 not finished as late as June. 



Second winter and summer. — Moults as adult. Dark form. — 

 Crown, back and sides of neck, upper -parts and throat much as 

 adult, but even in summer, feathers of back of neck not always 

 pointed and streaked yellow, some feathers especially on upper- 

 mantle and lesser wing-coverts with rufous or buff tips ; breast and 

 belly with more or less concealed broad bars and under tail-coverts, 

 axillaries and under wing-coverts varying but usually boldly barred 

 dark brown and buff. Pale form. — Back and sides of neck boldly 

 barred and streaked brown and whitish or buff, or buff streaked 

 brown ; feathers of mantle and scapulars tipped buff to whitish ; 

 breast, flanks and under and upper tail-coverts boldly barred dark 

 brown and white or pale buff, centre of breast and belly often white 

 not barred ; axillaries and under wing-coverts of both forms usually 

 boldly barred but sometimes only edged pale ; upper wing-coverts, 

 especially lesser, with some buff tips. 



Third winter and summer. — Like adults but even in summer 

 with some pale tipped feathers here and there on upper -parts and 

 often some barred on under-parts and white-breasted birds with 

 some brown-tipped feathers and sometimes some barred upper tail- 

 coverts and some under wing-coverts or axillaries with white 

 edgings or tips. 



Measurements and structure. — $ wing 305-328 mm., tail : (ad.) 

 central 175-215, outer 65-105 shorter, (juv.) central 118-140, outer 

 7-22 shorter, tarsus 42-45, bill from feathers 27-32 (14 adults 



VOL. II. 3 E 



