FOREST COMMUNITIES 433 



groups, chameleons, geckoes, agamids, and iguanids. The first men- 

 tioned have grasping feet and prehensile tails and are found in greatest 

 diversity in the forests of Madagascar and of Africa. The agamid 

 lizards, confined to the Old World, and the iguanid forms mainly in 

 the Americas, although sharply separated in anatomical characters, 

 have parallel series with astonishing similarities (Fig. 116). Both 

 families have ground-dwelling, riparian, and arboreal forms. In both 

 families arboreal forms have long tails and are laterally compressed 

 while the ground forms have relatively short tails and dorsoventrally 

 depressed bodies. A few varanids enter the rain-forest in the East 

 Indies. Snakes are not as abundant in these forests as would be ex- 

 pected from many popular accounts. 



Birds are the most striking inhabitants of the tropical rain-forest 

 and are present in all its strata. Since they are largely diurnal, their 

 richness of form and color stimulates interest as does the variety of 

 their habits. The birds of the upper forest seldom if ever come to the 

 ground; they are accustomed to slipping between the tangled branches, 

 but may have relatively poor powers of flight, and are limited to 

 forested regions. The parrots, with stronger flight, may be seen out- 

 side the forest, even though they are characteristic of the forest crown. 

 Ground birds also exist, usually smaller in size and dull in color, but 

 conspicuous because of their raucous voices. Wood hewers search over 

 the tree trunks like our common creeper. 



The forest birds frequently combine into groups out of their breed- 

 ing season; these groups may be composed of many species and even 

 of different genera. 42, 43 This sociability may be correlated with the 

 searching for food; thus among the birds of the tropical forest there 

 are many fruit eaters, parrots, doves, toucans, hornbills, musophagids, 

 cotingids, and others ; and the isolated forest trees with different times 

 for maturing fruit compel birds to roam from one to another. Hordes 

 of birds collect in trees with ripe fruit. Such flocks as wander together 

 are oriented with regard to each other by their loud voices. 



The woodpeckers are the most striking of the insectivorous birds. 

 They are particularly abundant in the American and Indian tropical 

 forests, while Africa has relatively few. The ground birds eat mainly 

 insects and are entirely characteristic of the shaded tropical forests, 

 whose moist dimness is essential to them, so much so that they are 

 sometimes called the "shadow birds." 44 Birds of prey are sparingly 

 encountered within the forest; nectar-feeding hummingbirds are abun- 

 dant. 



Since mammals are nowhere so abundant in the forests as in the 

 grasslands, most of the forest negroes of Africa are forced to practice 



