ISLAND COMMUNITIES 521 



nesting sites for great colonies of sea birds, which gather for their 

 breeding season from wide areas. 



The reduction of the biotic pressure makes it possible for insular 

 birds to develop unusual colorations. Albinism is most frequent in 

 Old World quail and blackbirds in the Azores; 16 in Iceland, albino 

 ravens are abundant; and white ravens may even exceed the normal 

 individuals in numbers in the Faeroes. 17 Albinism is frequent in land 

 birds in New Zealand. 18 The evolution of birds-of-paradise in New 

 Guinea and the adjacent islands may be explained in part by this 

 factor. The absence of predaceous mammals, monkeys, and large birds 

 of prey makes possible the frequent development of flightless birds in 

 islands, which is so remarkable a phenomenon in New Zealand and 

 the associated islands, in the Mascarene Islands, and in some degree 

 in various other localities. The parallelism in loss of power of flight 

 is continued in a number of forms in the loss of coherence of the 

 feathers, not only in the ratite birds but also in the extinct dodo, the 

 ralline Ocydromus and Cabalus of the New Zealand area, and the kagu 

 of New Caledonia. 



Extreme development in size is to some extent characteristic of 

 insular birds, correlated with Sightlessness and perhaps with the con- 

 sequent saving in energy expenditure. A great number of unusually 

 large birds of diverse groups are known from the New Zealand region 

 and from the Malagasy Islands, most of them recently extinct, and 

 some, like the dodo and solitaire, and the relatively gigantic Mauritian 

 parrot, Lophopsittacus mauritianus, 19 known only from fragments or 

 from drawings, since they became extinct within a few years of the 

 discovery of their islands by Europeans. 



Insular reptiles, especially tortoises and lizards, frequently reach 

 unusual proportions, but many of these are relicts rather than insular 

 developments. The largest existing land turtles are confined to the 

 Galapagos and to islands in the Indian Ocean. Fossil remains of equally 

 large forms are, however, known from continental deposits. The larg- 

 est living lizard, Varanus komodoensis, is confined to Komodo, Rindja, 

 and Flores Islands in the Dutch East Indies but seems plainly to be a 

 remnant of a form once more widespread. The large scincid lizard of 

 the Cape Verde Islands, Mabuya coctaei, and the large geckos and 

 skinks of New Caledonia suggest that a real connection between in- 

 sularity and large size exists, at least in some animals. 



Among other characteristics of oceanic island faunae related to 

 their isolation is the fact that they are distinguished by having dis- 

 proportionately developed taxonomic groups in which one or a few 

 basic types have undergone adaptive radiation and come to fill unduly 



