ANTARCTIC ZOOGEOGRAPHY 37 1 



birds the penguins and sheathbills are both southern hemisphere 

 groups, though the former have an extensive distribution in tem- 

 perate and even in equatorial latitudes. Several genera of sea mam- 

 mals, including four seals and the pygmy right whale (Neobalaena) , 

 are peculiar to the waters of the far south and have been made the 

 criteria of a distinct marine area, the Notapelagia of Sclater.^^ On 

 the whole, however, the Antarctic birds and mammals are character- 

 ized rather by high specialization of structure and habits than by 

 fundamental remoteness from more northerly stocks. At least two 

 representatives among birds, namely the species complex of the skua 

 gulls (Catharacta) and the silver-gray fulmar (Priocella antarctica) , 

 might almost be regarded as bipolar, for closely related forms of 

 these birds inhabit high latitudes in each hemisphere. The genus 

 name Priocella perhaps unjustifiably obscures the very close relation- 

 ship of this southern petrel with Fulmarus. There seems to be no 

 common meeting ground of the northern and southern skuas and 

 fulmars, respectively, in tropical and temperate seas. These sea fowl 

 therefore fulfill the requirement of completely discontinuous range 

 demanded by the bipolar hypothesis, though we should scarcely be 

 justified in applying the original interpretation to such mobile crea- 

 tures as sea birds. 



Distribution of Antarctic Birds 



As indicated above, only a handful of true land birds reach the 

 sub-Antarctic islands, and beyond the 55th parallel or thereabouts 

 there is not a single species. The only Antarctic birds, indeed, which 

 take even a portion of their food from anywhere except the ocean, are 

 the skua, the sheathbill, and the giant petrel (Macronectes) . All the 

 others are apparently incapable of even recognizing food substances 

 except in their watery element. According to Gain,^^ only about 32 

 species of birds penetrate beyond latitude 60° S., and most of these 

 are sub-Antarctic wanderers rather than polar species. 



But three species of birds can be considered exclusively Antarctic, 

 namely the south polar skua (Catharacta maccormicki) , the Adelie 

 penguin (Pygoscelis adeliae), and the emperor penguin (Aptenodytes 

 orsteri); and, as might be expected, these three are fully circum- 

 polar. The emperor penguin has been taken as far south as 78° S. 

 Even during the non-breeding period it clings to the northern border 

 of the fast-ice which fringes the Antarctic Continent. Apparently 

 it avoids for the most part the northwardly projecting peninsula of 



33 Berardius, another cetacean which Sclater placed in this group, has since been discovered in 

 the Arctic, so that the genus may be called bipolar. 



5' L. Gain: Oiseaux antarctiques (Deuxieme Expedition Antarctique Frangaise, 1908-1910, 

 commandee par le Dr. Jean Charcot: Sciences naturelles, Documents scientifiques, Vol. 2, pp. 1-200), 

 Paris, 1913. 



