ANTARCTIC ZOOGEOGRAPHY 373 



white examples are proportionately more numerous at the Antarctic 

 limit of the breeding range than in the sub-Antarctic islands. 



A third Antarctic group, likewise made up entirely of petrels, is 

 circumpolar throughout both the Antarctic and the sub-Antarctic. 

 It comprises the giant petrel, a storm petrel (Oceanites oceanicus), 

 the silver-gray fulmar, and the Cape pigeon {Daption capensis). The 

 first of these breeds even at the Falkland Islands. All four species 

 are famous oceanic wanderers, the Oceanites regularly migrating to 

 high latitudes in the North Atlantic during the northern summer 

 and the other three approaching or crossing the equator by way of 

 the cool littoral of western South America. 



A fourth group of somewhat heterogeneous composition is cir- 

 cumpolar in the sub-Antarctic belt but extends into the Antarctic 

 proper only via the South Orkney-South Shetland-Palmer Land ap- 

 proach. The birds of this group are the gentoo penguin {Pygoscelis 

 papua) , the macaroni penguin {Eudyptes chrysolophus) ,^^ the kelp gull 

 (Larus dominicanus) , the sub- Antarctic skua {Catharacta antarctica) , 

 which is a very different bird from the south polar skua, the blue petrel 

 (Halobaena) , and a storm petrel {Fregetta tropica). 



Finally, the last aggregation which can be called Antarctic is made 

 up of certain species characteristic of southern South America, the 

 Falklands, South Georgia, or the islands to the southward, which 

 penetrate into the adjacent parts of the south polar mainland. These 

 are the ringed penguin {Pygoscelis antarctica) , a tern {Sterna hirundi- 

 nacea), the sheathbill, and a shag {Phalacrocorax atriceps). The 

 zoogeographic importance of the Palmer Land peninsula and its 

 outliers as a connection with South America is evident. By this route 

 no less than ten species of birds have gained a local foothold on the 

 polar continent. Mere proximity does not wholly account for this, for 

 the extension of the great land projection toward the milder winds of 

 the belt of westerlies endows it with generally favorable life conditions. 

 It is probably the richest part of Antarctica, and Drygalski has lik- 

 ened the region to the west coast of Spitsbergen. 



The foregoing geographical grouping of Antarctic birds has been 

 adapted from Andersson,^^ who has also applied the same plan to 

 a discussion of the seals. Although based upon altogether insufhcient 

 collecting, it may serve as a skeleton to be clothed with further 

 observations. 



Many other species of penguins, Tubinares, etc., are exclusively 

 sub-Antarctic in their breeding ranges and are unknown south of the 

 northerly parts of the pack-ice region. The king penguin, several 

 albatrosses {Diomedea, Phoebetria, Thalassarche), the prions, or whale 



^' In the literature the crested penguin of West Antarctica has been incorrectly reported as another 

 species, Eudyptes chrysocome. 



^2 Work cited in footnote 31, above. 



