33 



flapping their wings wliilst so doing. It has been observed of 

 several species of Vultures that when soaring, their wings appear 

 to be perfectly free from any flapping or even any vibratory 

 motion ; when this is the case, the bird occasionally extends and 

 retracts its neck, which may perhaps be connected with inhaling 

 air to fill the air-reservoirs, with which the sternal regions of 

 these birds are abundantly supplied, and which doubtless 

 contribute to aid their gi'eat soaring powers. The Vultures 

 are also remarkable for their powers of discerning their prey 

 at very great distances ; and it has long been a disputed point 

 whether this power is due to the sense of smell, or to that of 

 sight. Many observations and experiments have been made 

 with the view of setting this question at rest, especially on the 

 two commonest American species — the Black Vulture and the 

 Aura. The result of these observations appears to indicate — 

 1st, that Vultures are often guided to the vicinity of their prey 

 when soaring at a great distance from it, by observing the 

 evolutions of other Vultures or carrion-feeding birds, which 

 may happen at the moment either to be flying at a less eleva- 

 tion, or from some other cause to be nearer to the spot where 

 the carcase is lying. 2nd, that at a moderate distance, 

 Vultiu'es have the power of perceiving and appreciating the 

 efiiuvium evolved fi'om dying animals and from decomposing 

 carcases, and that they are thus frequently guided to the vicinity 

 of the body from which such effluvium arises, even though it 

 be concealed fr-om sight, and' though the effluvium given out 

 may not be perceptible to the human organs of scent. 3rd, that 

 this power appears to take efi'ect rather at a short distance from 

 the carrion than in close propinquity to it, and that, conse- 

 quently, when the prey is concealed from view, the Vultures, 

 although attracted by this faculty to the vicinity of the carcase, 

 usually appear unable to ascertain its exact situation and posi- 

 tion without the aid of sight; this last result is, however, 

 less uniform than the two preceding ones ; one, if not more, 

 instances having occurred of the American Black Vulture 



