486 LAND ANIMALS 



for the emperor penguin (Aptenodytes forsteri) to breed in the ant- 

 arctic mid-winter. The eggs are laid toward the end of June, and the 

 young hatches out at the beginning of September. 24, 25 



Other sea birds nest with the penguins. The robber-gull {Catha- 

 racta) and the small sheathbill {Chionis alba) carry on a regular egg- 

 robbery. The giant petrel (Macronectes gigantea) and a cormorant 

 (Phalacrocorax atriceps) join the breeding colony. The three antarctic 

 petrels, Pagodroma nivea, Thalassoica antarctica, and the Cape pigeon, 

 Daption capensis, breed on inaccessible cliffs. 23 



Breeding places of sea birds in the tropics offer somewhat different 

 phenomena. The birds gather from wide areas to small, uninhabited 



islands. Their numbers may be vast 

 if suitable islands are far apart. 

 The breeding seasons of different 

 species may differ, or be successive, 

 since there is no requirement of sea- 

 sonal concentration of the breeding 

 activity. Thus on Laysan (26° N. 

 latitude in the Pacific) there are 

 sixteen species of breeding birds, 

 which distribute their breeding ac- 

 Skin- ^enveloping the egg tivities through the year. In July 



Fig. 126.-Brooding penguins, Apteno- and earl y August the tropic birds 

 dytes patagonica. After Murphy. (Phaethon) and terns (Sterna) are 



breeding; Oestrelata hypoleuca ar- 

 rives promptly between the fifteenth and eighteenth of August; these 

 in turn give way to the albatrosses in October, which arrive in such 

 numbers that every available space is taken and many are compelled 

 to go further for lack of room. 26 This phenomenon may help to explain 

 the varying breeding season of the same species on different islands. 

 The shear-water {Puffinus assi??iilis baroli) breeds in Tenerife from 

 February to April, in Porto Santo (Madeira) from March to May, and 

 in Montana Clare (Canary Islands) from May to June. The same is 

 true of the petrel Oceanodroma castro. 27 Such tropical breeding places 

 may exhibit a concentration of bird life equal to that of the bird islands 

 of the north. It is curious that the birds often sit with bills pointing in 

 the same direction and against the wind, which would otherwise ruffle 

 their feathers (Fig. 127) . The constant feeding operations of the parents 

 in the north are replaced by a single daily feeding, which frequently is 

 made at a particular time of day with pedantic regularity ; on Laysan 

 the albatrosses return with full crops between 3 and 4 p.m., while the 

 tropic bird feeds its young between 9 and 10 in the forenoon. This pro- 



