BIRDS 327 



if we take Port Blair as a centre we shall find that its average 

 distance in all directions north and east from Tenasserim (where the 

 Indo-Malayan fauna predominates), and north of this from the 

 Indo-Burmese sub-region, is less than half its distance from the 

 nearest point of the Indian sub-region. 



That so many of the characteristic birds of the Arakan Hills, 

 especially the Rasores, should be entirely wanting, we may partly 

 account for by the supposition that the mountains and the chain 

 of islands never were continuous, and that the same agency that 

 raised the Arakan Hills only raised portions of their continuation 

 above the sea-level, so that, therefore, the islands have never been 

 connected with Pegu. If, however, the groups first appeared and 

 have ever since remained as detached islands, it is inconceivable 

 how the great bulk of the work of colonisation should have gone 

 on from a region so distant while so little should have been done 

 from others less than half as far away. 



Colonisation in no ordinary sense, however, can explain these 

 facts. But the case of Sumatra, which, although only 80 miles 

 distant from Great Nicobar, and itself the first link of a great 

 chain, teems right up to Acheen Head with species unknown to 

 the Nicobars, is perfectly comprehensible in the light of our 

 knowledge of the deep sea existing between it and these latter 

 islands.* 



* The presence of a megapode in the Nicobars, a genus that occurs also in 

 the Indo-Malayan region, is the most interesting feature of the islands' avifauna. 

 Dr A. R. Wallace says, in The Distribution of Animals : "The Megapodidai are 

 highly characteristic of the Australian region . . . only sending two species 

 beyond its limits {M. cumingi and M. loivi in the Philippine and North-West 

 Borneo Islands), and another in the Nicobar Islands, separated by about 1800 

 miles from its nearest ally in Lombok. The Philippine species offers little diffi- 

 culty, for these birds are found on the smallest islands and sandbanks, and can 

 evidently pass over a few miles of sea with ease ; but the Nicobar bird is a 

 very different case, because none of the numerous intervening islands offer a 

 single example of the family. Instead of being a well-marked or differentiated 

 form, as we should expect to find if its remote and isolated habitat were due to 

 natural causes, it so nearly resembles some of the closely allied species from 

 the Moluccas and New Guinea, that had it been found with them it would not 

 have been thought specifically distinct. I therefore believe that it is prol^ably 

 an introduction by the Malays (Dr Guillemard states that this bird is often seen 



