132 IV, 12. 



character acts as a protection to the breast, which owing to its 

 form would be very weak, were it not amply covered.^* 



Below the breast lies the belly, extending, as in quadrupeds 

 and in man, to the vent and to the place where the legs are jointed 

 to the trunk. 



Such, then, are the parts which lie between the wings and the 

 legs. Birds like all other animals, whether produced viviparously 

 or from eggs, have an umbilical cord during their development, 

 but, when the bird has attained to fuller growth, no signs of this 

 remain visible. The explanation of this will be set forth in the 

 treatise on Generation and Development, but amounts to this, 

 that in birds the umbilical cord unites with the intestine, and is 

 not a portion of the vascular system, as is the case in the vivipara.'^ 



Some birds, again, are well adapted for flight, their wings being 

 large and strong. Such, for instance, are those that have talons 

 and live on flesh. For their mode of life renders the power of 

 flight a necessity, and it is on this account that their feathers are 

 so abundant and their wings so large. Besides these, however, 

 there are also other genera of birds that can fly well ; all those, 

 for example, that depend on speed for security, and all those 

 again that are of migratory habits. On the other hand some 

 kinds of birds have heavy bodies and are not constructed for 

 flight. These are birds that are frugivorous and live on the 

 ground, or that are able to swim and gain their livelihood in 

 watery places. In those that have talons the body, when stripped 

 of [its feathers and] wings, is small ; for the nutriment is con- 

 sumed ^^ in the production of these weapons and defensive ap- 

 pliances; whereas in birds that do not fly the contrary obtains, 

 and the body is bulky and so of heavy weight. In some of these 

 heavy birds the legs are furnished with what are called spurs, 

 which replace the wings as a means of defence. Spurs and 

 talons never co-exist in the same bird. For nature never makes 

 anything superfluous ; and if a bird can fly, and has talons, it 

 has no use for spurs ; for these are weapons for fighting on the 

 ground, and on this account are an appanage of certain heavy- 

 bodied birds. These latter, again, would find the possession of 

 talons not only useless but actually injurious ; for the claws 

 would stick into the ground and interfere with progression. This 

 is the reason why all birds with talons walk so badly, and why 

 694 a. 



