212 THE SKUAS 



action. Arctic-skuas attack in pairs. The common-gull makes com- 

 bined attacks, but the habit is less confirmed in some of its congeners, 

 and in them we should expect to find a development of the feigning 

 action, as also in other species of Skuas, except perhaps the great- 

 skua, whose larger size and formidable appearance may suffice to 

 inspire respect even in the breast of a fox. 



The fact that there are now no foxes in the Shetlands does not 

 affect the probability of the supposition that, in the case of the Arctic- 

 skua, the feigning instinct was developed as a defence against them 

 and similar enemies, provided we assume it to be an instinct, that is, 

 inherited from ancestors that were harried by predaceous mammals 

 either in Shetland or farther north. 



The great-skua begins laying usually in the second or third week 

 in May, the Arctic later, towards the end of the month or early in 

 June. Incubation is performed by both sexes, and lasts three to four 

 weeks, longer, of course, in the case of the larger species than the 

 smaller. Not much is known of the behaviour of the young, except 

 that they are prompt to quit the nest when alarmed, and after running 

 a certain distance, remain usually in a crouching position till picked 

 up ; they then show fight, using each its claws and beak more or less 

 viciously, according to its disposition. When teased, young Arctic- 

 skuas have been seen to " run off unsteadily across the heather, using 

 their wings to aid them." l 



The young are fed chiefly on fish, but insects and berries have 

 been found in the stomachs of the young Arctic-skuas. 2 The fish are 

 disgorged by the parent birds, those by the great-skua being often 

 left lying about the nest in a headless condition. In the neighbour- 

 hood of one nest Saxby found 39 full-grown herrings, all headless. 3 

 Near, or not far from, another Mr. E. Selous found 41 herrings or their 

 remains, and of these only 10 retained the head or any part of it. 4 It 

 may be that these headless fish are subjected to a double regurgitation, 



1 Ornithologist, 1896-7, p. 173 (R. Godfrey). See the " Classified Notes." 



1 Birds of Shetland, p. 352. 4 Bird Watching, p. 116. 



