BIRDS OF THE SEASHORE 107 



black. Length 21 in. Female similar. Young much 

 like the adults. Nestling covered with brownish grey 

 down. 



Language. A cry resembling " skui," hence Skua. 



Habits. Very strong and swift on the wing, and when 

 near its nest it swoops most menacingly round the in- 

 truder's head. Very predacious, and prefers rather to 

 rob Gulls of food they have found than find it 

 itself ; it will even attack and kill other weakly Gulls. 



Food. Fish and animal matters found floating on the 

 sea or purloined from other birds. 



Nest. May. One brood. 



Site. In hollow in ground on high moorlands. 



Materials. Twigs, dry grass, moss, &c. 



Eggs. Two. Olive-brown, blotched and spotted with 

 dark brown and greyish brown. 



ARCTIC OR RICHARDSON'S SKUA 



(Stercorarius crepidatus}. 



The commonest Skua in these islands, being a regular 

 visitor to our coasts in autumn and spring. - It breeds 

 in the Shetlands, Orkneys, Sutherland, and Caithness. 



Plumage. Crown dusky. Cheeks, neck, and under 

 parts white, suffused with yellow ; remaining plumage 

 umber brown. Tail rather long and tapering. Bill 

 horn-colour. Legs and feet black. Length 20 in. 

 Female similar. 



Observation. There are two forms of this species, one 

 light (above described), the other dark. As these two 

 varieties interbreed, birds with plumage intermediate 

 between the light and dark forms are found. The young 

 are also subject to some variation in their immature 

 plumage according to the variety to which their parents 

 belong. Nestling covered with sooty-grey down, paler 

 below. These also vary according to the parents. 



Language. A cry like " mee " or " mee-awk." 



