56 INTRODUCTION. 



in any quantity, and thus it happened that the Owl, for con- 

 venience, was fed upon this diet. 



Besides such changes in their food produced by domesti- 

 cation, other changes from ihe same cause may be occa- 

 sionally observed. Some of the song birds will sing at night 

 if placed in considerable light. This may be seen exempli- 

 fied in some of the bird-shops of the metropolis, where, fre- 

 quently, not only in the spring, but also in the month of 

 November, (I have heard them on the 20(h of this last 

 month,) many of the song birds are as lively and harmonious 

 at nine o'clock at night as in any part of the day. 



Eirds, having no urinary bladder, as above stated, do 

 not eject the tluid secreted in the kidneys, in the same way 

 as the mammalia, they having no organ for such purpose. 

 The kidneys in birds are considerably elongated, and much 

 larger in proportion to their size than those in the mamma- 

 lia j this enlarged size has been supposed necessary in con- 

 sequence of there being little or no transpiration by the skin, 

 much of the fluids which pass off by this process in the 

 mammalia, passing off in birds, it is supposed, by means 

 of the kidneys; but the secretion from these glands is dis- 

 charged directly from them into the rcetum, and thence 

 ejected with the fajces, over which it may be seen, a 

 whitish substance, that afterwards assumes a chalky appear- 

 ance. The Ostrich has, however, it is sai<l, a sort of 

 urinary bladder. 



The manner in which birds sleep may also be noticed. 

 The Pie and Sparrow tribe, denominated by Mr. Vigors 

 Insessores or PercherSj usually sleep standing on one leg 

 upon some tree, bush, or other elevation, with the head 

 turned behind, and the bill thrust under the feathers on the 

 back, or under the wing. Indeed, these appears to be the 

 general habits of the whole race of birds in regard to their 



