SWAMPS AND SHORES 



485 



northward to the equator only in the cold waters of the Humboldt 

 current (see p. 386). 



The penguins are like the auks in many respects, owing to con- 

 vergent adaptive evolution, for they are not closely related. They are 

 skillful divers, with short wings which are used as oars, and which are 

 reduced to complete Sightlessness, which was also true of the extinct 

 great auk (Pinguinis impennis). The close-lying and oily plumage and 

 the short legs placed at the extreme rear end of the body give them a 

 similar appearance when sitting. Penguins feed on fishes, cuttlefishes, 





m 



Fig. 125. — Breeding place of the penguin, Spheniscus demersus, on Jutlen Island, 

 South Africa. Photo by Rudyerd Boulton. 



crustaceans, etc., secured by diving. The Adelie penguins, for example, 

 feed primarily on euphausids at certain seasons. The breeding places 

 are recognizable from afar by the odor of fish and ammonia. Where the 

 Adelie penguin breeds, the whole area is reddened by the pigment of 

 the ephausid crustaceans in the dung of the birds. At the beginning of 

 winter the breeding places are abandoned; the penguins range north- 

 ward in the sea, following the borders of the pack ice. Pygoscelis 

 adeliae migrates still further northward and does not return to its 

 breeding places before the regular breeding season, even if ice condi- 

 tions permit. 23 Like the auks, penguins have only a single egg (rarely 

 two) and brood this by pressing it into a featherless brood pocket 

 situated posteriorly on the belly, protecting it from below with the 

 feet (Fig. 126). This effective protection of the egg makes it possible 



