784 A PRACTICAL HANDBOOK OF BRITISH BIRDS. 



(i.e. 2nd and 3rd) straw-white but that of 4th often clouded with 

 brown especially in dark birds ; primary-coverts black-brown ; 

 rest of upper and under wing-coverts and axillaries in both forms 

 dark umber-brown. This plumage is acquired by complete body- 

 moult Jan. to April, but wing-feathers, wing-coverts and tail 

 appear to be moulted only once, commencing sometimes Oct., 

 usually Nov. and completing March or April. Body-moult to 

 winter commences sometimes Sept., but apparently usually takes 

 place Nov.-Dec. — N.B. Very few adults moulting to winter or in 

 winter plumage are available for examination. Winter. — Pale 

 form. — New feathers of crown, especially sides and round eye, black- 

 brown edged whitish ; back and sides of neck streaked and barred 

 to varying extent dark brown, tips sometimes rounded, sometimes 

 pointed and yellow ; lower-neck and upper -mantle barred dark 

 brown and pale buff ; feathers of mantle and scapulars dark brown 



The Arctic Skua (Stercoral his parasiticus). Distal portion of tails of— A. Adult. 

 B. Juvenile. 



margined white ; upper tail-coverts mostly broadly barred black- 

 brown and white ; chin spotted dark brown ; lower-throat and 

 upper-breast narrowly barred dark brown ; flanks and under tail- 

 coverts broadly barred black-brown and white. Dark form. — 

 Feathers of neck often rounded and without yellow tips, those of 

 upper -mantle often tipped rufous and some on under -parts obscurely 

 barred pale buff, but apparently sometimes there is very little 

 difference in winter and summer plumage. 



Nestling (Plate 11). — Closely covered with soft down with silky 

 hair -like tips. Rich umber-brown, paler and tinged greyish round 

 eyes, at tips of wings, on chin and in centre of under-parts. Some- 

 times blackish -brown rather paler on under-parts. Down is replaced 

 by juvenile feathers to tips of which it clings. 



Juvenile. — Varying considerably. Head and back of neck 

 brown-buff streaked black to uniform brown-black or sometimes 

 with feathers lightly tipped rufous ; mantle, scapulars and back 

 black-brown, feathers with tips varying in width of buff to rufous 

 and sometimes uniform black-brown with only a few inconspicuous 

 tips on scapulars ; upper tail-coverts black-brown with rufous 

 edges at tips and sometimes broadly barred buff and black-brown ; 

 under-parts varying from uniform black-brown except for a few 

 rufous tipped feathers on flanks and under tail-coverts to white 

 heavily tipped and barred brown, intermediates being buff-brown 



