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COLLEGE ZOOLOGY 



sapsucker (Fig. 322) is harmful, since it 

 eats the cambium of trees and sucks sap, 

 thus disfiguring and devitahzing fruit and 

 ornamental trees, and reducing the market 

 value of lumber. 



Perching birds 



More than half of all the living birds 

 known (about 8600 species) belong to the 

 order Passeriformes, the perching birds. The 

 passerine or perching birds are usually small 

 or of medium size, but they are the most 

 highly organized of the birds. Their feet are 

 four-toed and adapted for grasping. The 

 first toe or hallux is directed backward and 

 is on a level with the other three which are 

 directed forward. The nonsinging birds 

 have a syrinx which is poorly developed as 

 a musical apparatus; the tyrant flycatchers, 

 such as the kingbird (Fig. 330), phoebe, 

 and wood pewee, are examples. 



Figure 330. Kingbird on nest. Note crest and 

 sharp beak. Length SVi inches. (Photo by Merwin. 

 Courtesy of Nature Magazine.) 



Domesticated birds 



The common hen was probably derived 

 from the red jungle fowl, Gallus gallus, of 

 northeastern and central India. The varie- 

 ties of chickens that have been derived from 

 this species are almost infinite. Many varie- 

 ties of domesticated pigeons (tumbler, fan- 

 tail, pouter, etc.) have all descended from 

 the wild rock dove, Columba livia. Certain 

 variations such as the fantail occur; the 



breeder takes advantage of the opportunity 

 afforded by nature, and pigeons with this 

 type of tail are bred together until a new 

 variety is established. 



Geese are supposed to have been derived 

 from the graylag goose, Anser anser; most of 

 our domestic breeds of ducks have sprung 

 from the mallard, Anas platyrhynchos. The 

 common peacock, Pavo cristatus, of the 

 Indian peninsula, Ceylon, and Assam, has 

 been in domestication at least from the time 

 of Solomon. The guinea fowl, Numida 

 meleagris, is a native of West Africa; and 

 our domestic turkeys are descendants of the 

 Mexican wild turkey. 



Fossil and extinct birds 



The study of living birds is followed by 

 many professional zoologists, and amateur 

 bird students number many thousands. 

 However, the study of fossil birds, although 

 of great interest, is a very restricted field be- 

 cause so little of their fossil history is 

 known. 



It is customarv to divide birds into two 

 subclasses, the Archaeornithes or ancient 

 birds, and the Neornithes or recent birds, 

 containing all living birds and a number of 

 orders of fossil forms because of their like- 

 ness to modern birds. A few of the more 

 interesting fossil species are described in the 

 following paragraphs. 



Subclass Archaeornithes 



The two genera Archaeornis (Fig. 331) 

 and Archaeopteryx belonging to this sub- 

 class are known from two fairly complete 

 skeletons that were found in the lithographic 

 slates of Solenhofen, Bavaria, of the Upper 

 Jurassic period. Each was about the size of 

 a crow. They possessed teeth embedded in 

 sockets, forelimbs with three-clawed digits 

 and separate metacarpal bones, and a lizard- 

 like tail with large feathers on both sides. 

 Though reptilian features predominate in 

 the skeleton, the presence of feathers, indi- 

 cating warm blood, place these curious crca- 



