336 GEOGRAPHICAL ZOOLOGY. [part iv- 



a physical cause for this peculiarity of distribution. Pigeons 

 build rude, open nests, and their young remain helpless for a 

 considerable period. They are thus exposed to the attacks of 

 such arboreal quadrupeds or other animals as feed on eggs or 

 young birds. Monkeys are very destructive in this respect ; 

 and it is a noteworthy fact that over the whole Australian re- 

 gion, the Mascarene Islands and the Antilles, monkeys are un- 

 known. In the Indo-Malay sub-region, where monkeys are 

 generally plentiful, the greatest variety of pigeons occurs in the 

 Philippines, where there is but a single species in one island ; 

 and in Java, where monkeys are far less numerous than in Sumatra 

 or Borneo. It we add to this consideration the fact, that mam- 

 malia and rapacious birds are, as a rule, far less abundant in 

 islands than on continents ; and that the extreme development 

 of pigeon-life is reached in the Papuan group of islands, in which 

 mammalia (except a few marsupials, bats, and pigs) are wholly 

 absent, we see further reason to adopt this view. It is also to 

 be noted that in America, comparatively few pigeons are found 

 in the rich forests (comparable to those of the Australian insular 

 region in which they abound), but are mostly confined to the 

 open campos, the high Andes, and the western coast districts, 

 from which the monkey-tribe are wholly absent. 



This view is further supported by the great development of 

 colour that is found in the pigeons of these insular regions, cul- 

 minating in the golden-yellow fruit-dove of the Fiji Islands, the 

 metallic green Nicobar-pigeon of Malaya, and the black and 

 crimson Alcctrcenas of Mauritius. Here also, alone, we meet 

 with crested pigeons, rendering the possessors more conspicuous ; 

 such as the Lopholaimus of Australia and the crowned Goura of 

 New Guinea ; and here too are more peculiar forms of terrestrial 

 pigeons than elsewhere, though none have completely lost the 

 power of flight but the now extinct Dididse. 



The curious liking of pigeons for an insular habitat is well 

 shown in the genera Ianthcenas and Oalcenas. The former, con- 

 taining 11 species, ranges over a hundred degrees of longitude, 

 and forty-five of latitude, extending into three regions, yet 

 nowhere inhabits a continent or even a large island. It is 



