174 



Gl'LL GROUP 



immediately north of the j^rcat ice-barrier include those of the Arctic tern, 

 which is thus demonstrated to have, so far as is at present known, the 

 most extensive range in latitude of any known vertebrate. Nesting in 

 the highest north, where its range extends to latitude 82 , this tern, 

 when the duties connected with the breeding-season are over and the 

 short northern summer shows signs of coming to a close, wings its way 

 to the opposite pole, there to spend the southern summer feasting on 

 the organisms which abound in the sea immediately north of the 

 Antarctic ice-barrier, latitude 74 i' S. being the extreme range at 

 present recorded in this direction. Towards the close of the summer 

 these terns, which occur literally in thousands, are joined by flocks of 

 petrels and sooty albatrosses which have bred in lower Antarctic 

 latitudes, but are attracted by the same abundant food-supply at the 

 base of the ice-barrier. There may also be a certain number of non- 

 breeding petrels and albatrosses which pass the whole summer in 

 compan}' with the Arctic terns. That the latter does not breed in the 

 southern ocean may be considered certain, nor is any other kind of tern 

 known to inhabit the Antarctic continent. In Europe the breeding-range 

 extends as far south as latitude 50 , and in North America to latitude 4.<|.'. 

 The blood -red beak, coral -red legs, and pearl -grey under- parts 

 distinguish the Arctic from the common tern in summer-plumage ; 



and at all seasons the dark 

 band along the inner side of 

 the shafts of the primar\' quills 

 is much narrower and more 

 indistinct in the former than 

 in the latter. There is, more- 

 over, a greater difference be- 

 tween the summer and winter 

 plumages than is the case in 

 the common tern, since, in 

 addition to the partial loss 

 of the black cap by the in- 

 termingling of white feathers 

 on the forehead and crown, 

 the pearly grey under- parts 

 fade into white. Young birds in first plumage have the upper-parts 

 mottled with buff, and a buff tinge on the neck and flanks, the nape 

 above being blackish, and the forehead and crown white. The down\' 

 chick is hardly distinguishable from that of the common tern, although 

 the throat is somewhat darker-coloured. 



Vi>lN(; AKCTK Tl.KN- 



