x INTRODUCTION. 



the year. The males, with some exceptions, are as a rule larger 

 and more highly coloured. 



The voice organs are placed in a glottis, at the bifurcation at 

 the end of the wind-pipe, which is formed of entire rings of cartilage, 

 and the call of each bird is produced by peculiar sets of muscles 

 called the larynx. It is here, that that peculiar gift ot Nature, the 

 voice of birds, is formed, and this one of all other attributes dis- 

 tinguishes the class from all others in the animal kingdom. The air 

 contained in the cells of the lungs is the force used, while the wind- 

 pipe and the larynx with their contractions, or expansion or move- 

 ments in the gullet, contribute to the modulations and modifications 

 of the voice. By their song one knows of their happy and cheerful 

 life, and by it the male woos its mate. It is a language which is 

 not even known whether belonging to one family only, or generally 

 intelligible among the class. 



The nervous system in birds and the organs of the senses run rapidly 

 to high development. 



The sense of sight is also very highly developed in birds, and each 

 class and each family and sub-family will be found to be fitted with 

 organs developed to the extent of their wants and to suifc their 

 living condition. The eagle and the raptores generally soar out of 

 human sight, and yet they can see their prey notwithstanding the 

 immense distance. The owl is consigned as a night watchman r and 

 its organs of sight are so adapted that it can only distinguish objects 

 with greater facility in the dusk and when all nature is desirous of 

 repose. It is, however, compensated by a larger or more highly deve- 

 loped sense of hearing. The sense of sight is certainly extremely 

 keen and piercing, and this fact no doubt is an important 

 factor in the solution of the question of the manner in which thou- 

 sands of miles are traversed by birds in their annual migrations- 

 This must assist them. 



It is doubtful whether there is any special development of the 

 sense of taste in birds ; while that of smell, in the absence of any 

 reliable data, may be said to be, if at all, very little developed, except 

 in carrion feeders. 



