The Anatomy of Birds 21 



necessary in order that the bird may reach all parts of its body with the tip of its 

 bill, and secondly, that it may obtain food. Thus long legs and long necks go 

 together, or, as in the Sandpipers and Snipe, there is an increase in the length of 

 the bill, while Swifts, Swallows, and Goatsuckers, which capture their prey in 

 mid-air, have short necks. Swans, which do not dive, have much longer necks 

 than diving birds, or Geese, which feed largely on land, The very long neck of 

 the Darter is associated with its habit of suddenly straightening the neck and 

 impaling fish on its sharp bill. 



Usually the last two neck vertebrae bear free ribs, these being but the lengthen- 

 ing and freeing of the long processes running backwards from the sides of the 

 front of the vertebrae. That these are really ribs may be readily seen in a young 

 Ostrich, in which they are free, but while later on they become united with the 

 bodies of the vertebrae, the last two remain free, although they do not reach the 

 sternum. 



The thoracic region of a bird, the body proper, usually consists of a com- 

 paratively small number of vertebrae bearing long ribs, the foremost of which 

 are attached to the sides of the breast-bone. Water fowl, like the Loons, Auks, 

 and to a lesser degree Ducks, have the longest bodies, soaring birds the shortest. 

 Several of the vertebrae in the center of the series are fused or ankylosed together 

 to stiffen the body for flight, a free vertebra or two next the pelvis permitting 

 some motion here. 



The sacral vertebrae, or those to which the pelvis is attached, are really but 

 two, as in reptiles, or in rare cases three in number, but in front and behind are 

 added vertebrae from the back and tail region, the result being a long series of 

 vertebrae firmly united in one mass and furnishing ample attachment for the 

 pelvis and a firm support for the legs. The number of bones in this synsacrum, 

 as it is called, can only be clearly seen in young birds, but there may be from 

 twelve to as many as twenty. 



Finally comes the caudal series of free tail vertebrae, which may vary from five 

 to as many as ten, the average number being about six, and in all the higher 

 birds, or Neognathae, terminating in the flattened urostyle, to which the tail 

 feathers are attached. This bone in turn comprises four to six modified sections. 



The skull of a bird, roughly speaking, is divided into two parts, the beak and 

 brain case. The beak portion, which is very directly concerned in the getting of 

 food, is subject to many and great modifications ; the rear portion, being away 

 from direct modifying influences, is less altered, and here the palatal part of the 

 skull is of the most importance for purposes of classification, for the less a part 

 is subject to outside influences and the less a creature's habits have to do with 

 any part of the body, the less, theoretically at least, should that part be subject 

 to modification, and the more important it is for use in classification. 



There are two existing types of skull structure by which birds are divided into 

 two great groups, the Palaeognathae or Dromaeognathae, including the Ostriches 

 and their allies, and the Neognathae, Euornithes, or Eurhipidurae, which comprise 

 the vast majority of birds. These types are sharply marked, indicating that at 

 the very outset of their career, birds split into these groups, if indeed they may not 



