5 i8 



EVOLUTION OF BIRDS 



xviii. 7 



Order 8. Galliformes. Game birds 



These are mainly terrestrial, grain-eating birds, capable only of 

 short, rapid flights ; some of their structural characters and habits are 

 certainly primitive. The palate differs from both that of ratites and 

 of most modern birds, suggesting an early divergence. There is often 

 a marked difference in plumage, and sometimes in size, between the 

 sexes. The nest, usually made on the ground, is simple and the eggs 

 numerous, white, or spotted. The young develop very quickly after 

 birth. The order contains many successful types and is of world- 



^3== 



Fig. 310. Claws on hand of the hoatzin 



(Opisthoco??ius), I, in nestling; II, adult. 



(After Parker and Heilmann.) 



wide distribution. It includes Gallus, the jungle-fowl of India, and all 

 its domesticated descendants, also Phasianus and other pheasants, 

 Perdix (partridge), Lagopus (grouse), Meleagris (turkey), Numida 

 (guinea-fowl) and Pavo (peacock). The Megapodes or mound- 

 builders of the Australasian and east Indian regions lay their eggs in 

 mounds of decaying leaves and earth. In Opisthocomus, the hoatzins 

 of tropical South America, one of the few tree forms, the young 

 possess well-marked claws on the digits of the wing (Fig. 310), which 

 they use for climbing. These claws are usually considered to be a 

 secondary development ; their resemblance to the claws of *Archaeo- 

 pteryx is remarkable. 



Order 9. Gruiformes. Rails and Cranes 



The rails are mostly secretive, terrestrial birds, compressed laterally 

 and often living in marshy country and having an omnivorous diet; 

 common British members are the coots (Fulica) and moorhens (Gal- 

 linula). They run, swim, and dive easily, but are poor flyers; they 

 build rather simple nests and lay numerous, often dark-spotted eggs. 

 Crex (the corncrake) and other landrails are of more terrestrial 

 habit. The cranes (Grus) are long-legged birds found in swamps 



