﻿48 ON THE CLASSIFICATION OF BIRDS. 



because it is not only bare of feathers, but the orifice 

 appears to have a prominent rim, lengthened into a 

 wattle, which hangs down on each side of the neck. The 

 conch of the ears in the common barn owl, and a few 

 others, have a small lid or operculum, which partially 

 closes the aperture ; but this appendage lies perfectly flat, 

 and is entirely hid by the surrounding feathers. In 

 describing the parts or colours of a bird, the term " ear " 

 must be considered as not strictly applying to that organ, 

 but to the ear feathers, or those which cover the orifice 

 of the ear itself. 



(52.) We know, either from facts, or from certain 

 indications, that the sense of smell is very highly de- 

 veloped in some tribes, and but very slightly in others. 

 It has generally been supposed that vultures were at- 

 tracted to their food by their sense of smell, and not by 

 their sight; and this error has given rise to some ingenious 

 arguments and unjustifiable personalities against Mr. 

 Audubon, — the first, we believe, who called this supposed 

 truth in question. The results, however, have been such as 

 to enable that gentleman to silence his opponents, and 

 to establish, in the most complete manner, the accuracy of 

 his first assertion. We must, therefore, consider that the 

 toucans, above all other birds, are the most highly gifted 

 in this respect, — a fact which is not only established by 

 their economy, but also by their structure ; the latter 

 evidence being wholly wanting in the case of the vultures, 

 whose nostrils have nothing in them to sanction a belief 

 of their being more highly sensitive than those of ordi- 

 nary birds. This great development of the olfactory 

 nerves in the toucan is concentrated in the bill, which 

 is entirely filled with a cellular tissue of nerves, somewhat 

 resembling the webs of those spiders which are found in 

 dark corners, being crossed and interlaced in different 

 directions by thread-like nerves, all of which communi- 

 cate to the two lateral openings of the nostrils, placed, 

 not in the substance, but on the sides of the bill, close 

 to the front of the head. This extraordinary gift of 

 smell enables these birds to discover the nests of others, 



