262 THE BIRDS OF THE BRITISH ISLES. 



its piratical habits are the same. It is said to fish at times for 

 itself, and will feed on carrion, small birds, and, in its breeding 

 quarters, mammals and berries. The note is harsh, and E. T. 

 Booth, who kept the bird in captivity, found that the young, 

 at any rate, had a variety of screaming and whistling calls. 



The age variation of this and other skuas is puzzling ; almost 

 every bird seems to depart from the normal. Booth was of 

 opinion that maturity was not attained until the fifth year, but 

 little is known of the plumage changes of birds in the free state. 

 The mature bird has the head black on crown and nape, and 

 the cheeks and neck, where the feathers are pointed, streaked 

 or suffused with yellow. The back, wings, and tail are umber- 

 brown, the breast and front of the neck white, and the lower 

 abdomen brown. Immature birds are brown above and below, 

 barred and mottled with rufous and brown, but birds showing 

 more or less elongated tail feathers, and therefore approaching 

 maturity, have a wide pectoral band, which in younger birds is 

 almost self brown, but in those a little older is formed of brown 

 streaks and blotches. The primaries have white bases, and 

 the white extends further on the inner web than in the Arctic, 

 a useful distinction in immature birds. The bill in adult birds 

 is greyish black, bluer on the cere, but browner in young birds ; 

 the legs are brown, but often show bands or blotches of blue-grey, 

 a sign of immaturity ; and in the young, as in other skuas, the 

 webs usually differ in colour from the tarsi and toes. The irides 

 are dark brown. Length, 21 ins. Wmg, 14-5 ins. Tarsus, 2 ins. 



Order ALCIFORMES. 



Family ALCID^. Auks. 



Stout, short-winged, web-footed diving birds. Bills variable 

 in shape ; legs set far back and short ; hind toe absent. 



