VITAL ENERGY OF BIRDS. 571 



and that of a young guinea pig about six ounces, 

 while it is worthy of notice, that they are both 

 granivorous animals. In accordance with these 

 data, which can be regarded only as approxima- 

 tions to the truth, Moubray says, that the domes- 

 tic pigeon requires 1 oz. 2 drs. of solid barley per 

 day ; so that if we estimate the average weight of 

 pigeons at 12 oz. they must digest about T V of 

 their whole weight every twenty-four hours. It 

 therefore follows that the composition of fowls is 

 renewed in a period not much exceeding twenty 

 days, and that of pigeons in a much shorter time, 

 as might be inferred from the rapidity of their 

 growth, which is remarkable in all the feathered 

 tribes. 



The brain and nervous system are also more 

 highly developed in small, than in the larger 

 species of birds ; especially in the canary, bull- 

 finch, and several of the songsters, including the 

 parrot tribe, and more so in some of them, than in 

 any other description of animals, not even except- 

 ing man.* Hence the remarkable acuteness of 



* On the authority of Haller and Cuvier, Mr. Lawrence gives 

 the weight of the brain in several species of birds, compared with 

 that of the whole body, as follows : 



Canary 1 . . 14 



Sparrow 1 . .25 



Chaffinch 1..27 



Fringilla 1..27 



Red-breast . , 1..32 



Blackbird 1.. 68 



Falcon 1..102 



Duck 1..257 



Eagle 1..260 



Goose , 1..360 



Nor is it unworthy of notice, that in the ostrich, cassowary, 

 swan, condor, and turkey, the relative size of the brain is still 

 less, corresponding with their well known stupidity. 



