AVES 



3SS 



4. Pelvic girdle and hind limbs adapted to support the body on 

 the ground. 



5. Respiratory system developed to produce a higher tempera- 

 ture than in any other animal. 



6. Absence of teeth. 



7. Loss of the left aortic arch. 



8. Right ovary and oviduct lost. 



9. Poorly developed olfactory organs. 



10. Extraordinary development of the eyes. 



Temperature ^ is lower in most lowly organized birds. There is 

 a progressive gradation to the higher birds. The apteryx or kiwi, a 

 wingless bird of New Zealand, has a temperature of 37.9° C. (100.2° 

 F.). The emu, cassowary and penguin have a temperature of 

 39.° C, the sparrows and warblers from 42° C. to 44° C. (107.6° 

 F.), the common fowl, 40.6° C. The average of sparrows is 109.9° 

 F., which is 10° above the temperature of man. (Figure 199.) 



Feathers have a hollow, transparent barrel, or quill, continuous 

 with the shaft or rachis. The shaft is opaque, quadrangular in 

 cross section and filled with a pithy substance. From the shaft 

 above the quill arise lateral branches, known as barbs or rami. 

 Barbs give off barbules and these in turn give off the barbicels 

 which are hooked processes. The hooked processes produce the 

 web and furnish it strength to resist or act upon the air. From the 

 underside of some feathers at the juncture of the quill with the web- 

 bearing portion is a secondary feather, the after shaft. There are 

 three kinds of feathers: (i) Contour feathers (complete). (2) 

 Down feathers, soft shaft, no barbs, serve to retain heat. Some 

 have no shaft. (3) Filoplumes, degenerate, hairlike with few or no 

 barbs. 



Feathers are derived from cornification of the inner layer of the 

 epidermis. The papillae consist of external epidermis and internal 

 dermis, the latter furnishing nutriment to the growing feathers. 

 Epidermal scales of the birds arise similarly from papillae. 



Birds shed their old feathers. They molt in the fall and have a 

 partial molt in the spring b7-eeding-season. They acquire a new set 

 of feathers from the follicles. Some also shed parts of their claws, 

 bill and bill membranes. (Figure 200.) 



^ For further data on temperature and color, see Knowlton's Birds of the World. 



