FORM OF THE BIRD. 225 



standing variations which correspond with the different apti- 

 tudes for flight with which each species is endowed, we find 

 that it is about one- sixth of the whole weight in the greater 

 number of birds. 



jName 01 bpeciBS. 



Weight = p 

 vxrammes. 



Surface of 

 Wings = 2a. 

 Square centi- 

 metres. 



iiaiio = 



V 



Vultur . . . . 



1663-94 



3131 



4:'722 



Vultur cinereus . . . 



1535-00 



3233 



4-929 



Falco tinnunculus 



128-94 



642 



5-015 



,, minor . 

 Falco Kobek 



147-36 



546 



4-424 



282-44 



970 



4-747 



Falco sublatio (?) . . . 



509-62 



1684 



5-138 



Falco palustris . • 



208-76 



1188 



5-810 



Falco milvus • • 



620-14 



1904 



5-117 



Strix passerina . . 



122-80 



394 



3-993 





128-94 



442 



4-162 



Saxioola cenanthe • 



56-05 



125 



2-922 



Alauda cristata . • 



36-80 



202 



4-273 



Corvus comix . 



374-54 



1156 



4-717 



Upupa epops . . . 



49-12 



329 



4-952 



Merops apiaster. 



18-30 



117 



4-105 



Alcedo ispida . , . 



82-89 



270 



3 769 



Alcedo afra (?) . 



85-96 



288 



3-845 



Columba vinacea . . . 



112-00 



292 



3-545 



Vanelliis spinosus 



159-64 



636 



4-649 



Glareola . . , . 



95-17 



343 



4-056 



Buteo vulgaris . 



785-00 



1651 



4-405 



Perdix cinerea . , . 



280-00 



320 



2-734 



Sturnus vulgaris 



78-00 



202 



3-326 



Corvus pica . . . . 



212-00 



540 



3-906 



>» >» ... 



275 00 



690 



4 039 



Hirundo urbica , . . 



18-00 



120 



4-180 



Turdus merula . 



94 00 



230 



3-335 



In conclusion, each animal which sustains itself in the air 

 must develop work proportionate to its weight ; it ought, for 

 this purpose, to possess muscular mass in proportion to this 

 weight ; for, as we have already seen, if the actions performed 

 by the muscles of birds are always of the same nature, these 

 actions and the work which they perform will be in proportion 

 to the mass of the muscles. 

 11 



