18 ANIMAL LIFE AND SOCIAL GROWTH 



of the breeding season without being impressed 

 with the prodigality of nature. The thousands 

 of birds in the air and on the ground show that 

 the birds are locally extremely successful, yet 

 everywhere one sees dead nestlings, broken eggs, 

 nests that have been flooded, others deserted for 

 no obvious cause with the clutch of eggs only 

 partially completed; while all around are evidences 

 of a rate of avian infant mortality that is appalling. 

 There can be no question but that the physical 

 conditions within the habitat do set off different 

 animal communities for within easy walking 

 distance of this prodigality, one comes out on the 

 desert paucity of an almost entirely distinct 

 community. 



The major animal habitats just listed occur on a 

 world wide scale and while the habitat conditions 

 are similar in different parts of the world, and the 

 physiological requirements which the animals 

 make of their surroundings are also similar, it 

 does not follow that the animal life is the same in 

 the different world areas which present essentially 

 similar habitats. This is particularly well illus- 

 trated by the conditions found in the tropical 

 rain-forests, the "jungles" of popular writings. 



These extend in a wide belt in the rainy regions 

 around the equator. They present a strikingly 

 similar picture of luxuriant plant growth which 



