92 MENTAL EYOLUTIOX IN ANIMALS. 



The anatomical difficulty of accounting for this fact I need 

 not wait to consider. I am myself inclined to think that the 

 sense of hearing in birds (at all events of some species) is 

 likewise highly delicate with reference to the intensity of 

 sound. My reason for so thinking is that I have observed 

 Curlews dig their long bills up to the base into smooth 

 unbroken surfaces of sea-sand left bare by the tide, in order 

 to draw up the concealed worms. Under such circumstances 

 no indication can be given by the worm of its position to any 

 other sense of the curlew than that of hearing. Similarly, I 

 suspect that the common Thrush is guided to the worm buried 

 beneath the turf by the sense of hearing, and my suspicion is 

 founded on the peculiar habits of feeding shown by the bird, 

 which I have described elsewhere.* 



The sense of smell in Birds is in advance of that of 

 Eeptiles, but not to be compared with its excellency in 

 Mammals ; for the old hypothesis that vultures find their 

 prey by the aid of this sense has been abundantly disproved.! 

 The sense of taste in Birds is likewise very obtuse as com- 

 pared with this sense in Mammals ; and as compared with 

 the same class they are also defective in their organs of 

 touch. Indeed, the parrot tribe is the only one in which 

 this sense is well or specially provided for, except the ducks, 

 snipes, and other mud-feeding species, in which the bill is 

 specially modified for this purpose. 



If we regard Mammals as a class we must say that, with 

 the exception of the sense of vision which reaches its 

 greatest supremacy in Birds, aU the special senses are more 

 highly developed than in any other class. This is more 

 particularly the case with the senses of smell, taste, and 

 touch. 



The sense of smell reaches its highest perfection among 

 the Carnivora and the Euminants, and, on the other hand, is 

 totally absent in some of the Cetacea. Any one accustomed 

 to deer-stalking must often have been astonished at the pre- 

 cautions which it is needful to take in order to prevent the 

 game from getting the " wind " of the sportsman ; indeed to 

 a novice such precautions are apt to be regarded as implying 

 a superstitious exaggeration of the possibilities of the olfac- 



* Nature, vol. xv, pp. 177 and 292, wliere also see in more detail my 

 observations on the feeding habits of the curlew, 

 t See Animal Intelligence, pp. 286-7. 



