THE SKUAS 225 



on Steadily. The wings, when raised above the back, seem, indeed, to 

 indicate heightened emotion at all times in the life of the skua while 

 on land. Both sexes indulge in an attractive aerial display: sometimes 

 soaring together in circles; or one bird will make a spectacular dive, 

 or will perform an amazing twisting tumbling evolution in mid-air, 

 symbolic of the piratic chases at sea. The swift downward dive is 

 turned upon the human intruder as he crosses the breeding territory, 

 and he will be persistently dive-bombed until he leaves the area, and 

 perhaps struck on the head. The great skua also makes a frontal attack, 

 by a low approach over the ground, upon man, ponies, sheep, dogs and 

 other large animals, which is rather terrifying to face. This skua will 

 strike with determination, and often with successful results, at sheep, 

 even clinging to the wool and beating its wings about the head of the 

 intruding animal. The arctic and long-tailed skuas are adept at injury- 

 feigning in order to draw away from the nest the unwanted visitor; 

 the adult staggers over the ground with wings trailing as if they were 

 broken, but rather spoils the effect — at least for the human observer — 

 by rising into the air occasionally before resuming the display. William- 

 son (1929) considers that this is probably derived from primitive food- 

 begging and courtship actions. 



Great and arctic skuas nest in colonies, often of large size (500-750 

 pairs of great skua on Foula, Shedand, 1951). They are more sociable 

 than the pomarine and long-tailed skuas which scatter their nests 

 more widely on the tundra. The skua prepares a hollow for its nest, 

 but adds very httle material as a lining. The usual clutch is two, 

 occasionally one, exceptionally three, eggs. These are protectively 

 coloured: brown or grey, splotched with irregular dark brown spots. 

 In all respects the incubation resembles that of the gulls: it is by both 

 sexes, and of the same duration, 26-29 days. The new-born skua is 

 covered with a dark unmottled but protectively coloured down. It 

 is more precocious than the gull chick, develops rapidly and leaves 

 the nest early, being at first jealously attended by the adults. Skuas 

 may attack and kill chicks belonging to neighbours, but there does 

 not seem to be any record of that cannibalism within the family 

 circle found in the gulls. At one nest on Fair Isle the parents continued 

 to give the injury-feigning or lure display for five days after the death 

 of their single chick (or, as Wilhamson (1951) puts it, "the normal 

 parental response to intrusion persisted for some 5 days after all 

 biological need for it had ceased to exist.") This chick was eleven 

 days old, and the disturbing distractive behaviour of the adults is 



