74 



The Bird 



The remaining vertebrae, those of the upper and lower 

 back, are ver^^ different from those of the neck. The 

 flexible neck enables the bird to reach all parts of its 

 plumage with its beak, and to pick up food from the 

 ground or from twigs overhead, but the all-important 

 function of flight must be provided for by means of a 



Fig. 51. — White-throated Sparrow, three inches tall, with fourteen neck vertebrae. 



(Compare with Fig. 52.) 



rigid body-frame. In re])tiles and in the embryos of 

 birds only two pelvic vertebrae are fused together, but 

 in adult birds many dorsal and caudal vertebrae (as many 

 as 23 in some cases) are fused into a single bone. Thus 

 the rib-bearing upper back vertebrae are partially fused 

 together, and below them those of the lower back have 

 merged until it is difficult to realL-^e that this portion of 



