178 A. L. V. Manniche. 



with a lengthy fierce war-whoop an intruding neighbour in rapid 

 flight. 



The smaller birds hate the Skua, which is an expert egg-thief. 

 Especially the Turnstone is indefatigable in its pursuit of the detested 

 enemy. 



The Skua itself seems to fear but few enemies; though the 

 Polar Fox certainly values the Skuas eggs and young ones, and the 

 Gyrfalcon undoubtedly likes to feast upon the latter, the enraged 

 Skua-couple are as a rule able to scare them both off. 



The adult birds may be told by their two fully grown elongated 

 central tail feathers, which are of equal length, by the unmixed 



Fig. 18. Buffon's Skuas. 



slate grey colour of the back, by the black head and the unspotted 

 white fore breast. 



No external ditïerence between the sexes is noticeable. Birds in 

 full plumage vary a good deal with regard to the yellow colour of 

 the neck, which may be more or less intense, and furthermore the 

 extent of the slate-grey part of the abdomen may vary a good deal. 



The plumage of those immature birds, which in 1906 and 1908 

 were observed, varied extremely. While some of them still wore 

 many remnants of the plumage of the young and but slightly 

 elongated central tail feathers, some individuals — most likely two 

 years old — came very near to the appearance of the adults and 

 only their two unequally elongated tail feathers marked the difference. 



In every age the colour of the feet is the same: Tarsus blue, 

 the heels with black markings, toes and webs entirely black. 



