ARCTIC SKUA. 113 



The two species restricted to the genus Stercorarius are small Skuas with slender 

 bills, weak legs and feet (comparatively), long wings, and very long central tail- 

 feathers, acuminate, and attenuated into long streamers in the subgenus Atalo- 

 lestris. In the subgenus Stercorarius the tail does not exceed the wing, but is about 

 equal to it. 



79. Stercorarius parasiticus. ARCTIC SKUA. 



[Larus parasiticus Linne, Syst. Nat., 10th ed., p. 136, Jan. 1st, 1758 : coasts of Sweden. 



Extra -limital.] 



Mathews, Vol. II., pt. 5, pi. 124, Jan. 31st, 1913. 



Stercorarius parasiticus visitori Mathews, Austral Av. Rec., Vol. II., pt. 7, p. 126, Jan. 28th, 



1915 : Sydney, New South Wales. 



DISTRIBUTION. Australia. Winter visitor. 



Adult : dark phase. General colour above and below sooty-black with white 

 shafts to the primary -quills ; the lanceolate feathers on the sides of the neck rufous- 

 brown, nostril plumes dull white ; bill brownish-horn colour, tip black ; tarsi and 

 toes black. Total length 525 mm. ; culmen 32, wing 333, tail 212, tarsus 50. 



Adult: light phase. Differs from the dark phase in having the breast and 

 abdomen dull white like the sides of the head ; cheeks, throat, and fore-neck pale 

 brown ; hind -neck pale brown with straw-coloured shaft-streaks. 



Female. General colour above smoke-brown with a hoary tinge ; the feathers 

 at the base of the fore-head whitish and those on the fore-part of the head with pale 

 edges, hinder crown and nape uniform brown somewhat darker than the back ; 

 the feathers on the hind-neck, grey at the base and fringed with isabelline at the 

 tips ; the feathers on the mantle margined with pale umber as also are some of the 

 short scapulars, but rather darker ; marginal upper wing-coverts fringed with 

 whitish or isabelline ; inner webs of the primary- and secondary-quills white on the 

 basal portion, the shafts of the primaries flattened in structure and conspicuously 

 white in colour, but becoming dark at the extreme tips ; upper tail-coverts white, 

 more or less tinged with isabelline, banded and very slightly tipped with brown ; 

 tail white at the base the white decreasing in extent on the outer feathers and 

 brown at the tip, somewhat darker on the two central feathers which are extended 

 beyond the lateral ones and pointed in shape ; fore-part of the face including the 

 eye smoke-brown ; chin dull white ; the feathers of the throat and sides of the hinder 

 face white at the base with a pear-shaped mark of brown at the tips ; fore-neck 

 and sides of the upper-breast almost uniform brown ; remainder of the under- 

 surface white barred and fringed at the tips of the feathers with brown, narrowly on 

 the middle of the breast and sides of the abdomen, and broadly on the sides of the 

 body, flanks and under-tail coverts ; axillaries also broadly banded and more or 

 less isabelline as well as white ; under wing-coverts isabelline irregularly marked 

 brown or ash-brown, some of the feathers on the margin of the wing are only fringed 

 with white ; quill-lining white at the base and ash-brown on the apical portion ; 

 lower aspect of tail brown, becoming white towards the base. Eyes and bill black ; 

 tarsus pale blue, toes and webs black. Total length 455 mm. ; culmen 33, wing 310, 

 tail 169, tarsus 45. 



Immature male : dark phase. Dark brown above, the small coverts along the 

 edge of the wing margined with fulvous, the head and neck all round very similar in 

 colour, which colour is spread, more or less, over the breast ; remainder of under- 

 surface rufous or rust-brown, becoming almost black on the under tail-coverts, 

 which have slightly pale edges. 



Immature: light phase. Upper-surface greyish-brown, the feathers having 

 rufous edgings, the head and neck streaked with rusty-brown, sometimes rufous, 

 the neck paler than the head ; the under-surface irregularly barred, more or less 

 distinctly with brownish bars. Individual variation very pronounced. 



