162 AVES. 



which we can have no idea, and from the most ancient times has caused to be attri- 

 buted to them, by superstitious persons, a power of announcing future events. It is 

 doubtless upon this faculty that the instinct depends which [periodically] agitates 

 migratory Birds, and impels them to direct their course towards the equator when 

 winter approaches, and pole-ward at the return of spring.* They are not devoid of 

 memory, and even imagination — for they dream ; and every body knows with what 

 facility they may be tamed, taught [in numerous instances] to perform various services, 

 and to retain airs and words. 



DIVISION OF THE CLASS OF BIRDS INTO ORDERS. 



Of all classes of animals, that of Birds is the most strongly characterized, that in 

 which the species bear the greatest mutual resemblance, and which is separated from 

 all others by the widest interval. 



Their systematic arrangement is based, as in the Mammalia, on the organs of man- 

 ducation or the beak, and on those of prehension, which are again the beak, and more 

 particularly the feet. [The configuration of the sternal apparatus, also, (which we 

 have illustrated by numerous figures,) and the modifications of the digestive and some- 

 times vocal organs, supply highly important characters on which to ground the 

 subdivisions.] 



One is first struck by the character of webbed feet, or those wherein the toes are 

 connected by membranes, that distinguish all swimming Birds. f The backward position 

 of their feet, the elongation of the sternum, the neck, often longer than the legs, to 

 enable them to reach below them, the close, shining plumage, impervious to water, — 

 altogether concur with the feet to make good navigators of the Palmipedes. 



In other Birds, which have also most frequently some small web to their feet, at 

 least between the two external toes, we observe elevated tarsi ; legs denuded of feathers 

 above the heel-joint ; a slender shape ; in fine, all the requisites for fording along 

 shallow water, in search of nourishment. Such, in fact, is the regimen of the greater 

 number ; and, although some of them resort exclusively to dry places, they are never- 

 theless termed Shore-birds or Waders. 



Amongst the true land-birds, the Gallinacece have — like our domestic Cock — a heavy 

 carriage, a short flight, the beak moderate, its upper mandible vaulted, the nostrils 

 partly covered by a soft and tumid scale, and almost always the edges of the toes 

 indented, with short membranes between the bases of those in front. They subsist 

 chiefly on grain. 



Birds of prey have a crooked beak, with its point sharp and curving downward ; 

 and the nostrils pierced in a membrane that invests its base : their feet [save in the 

 Vulture group] are armed with stout talons. They live on flesh, and [the Vultures 



* It is certain, however, that the rapid enlargement of the sexual 

 organs is the immediate stimulant to migration in the spring; while 

 decline of temperature, most generally, is the directly predisposing 

 agent in the autumn : this is manifest in the case of migratory Birds 

 kept in confinement. The instances of the Swift, and tidult Cuckoo, 

 retiring southward at the hottest season of the year, are more difficult 

 of explanation, and indicate some ulterior agency not hitherto divined ; 

 though they do not affect the multitudinous observations, which con- 

 clusively prove the influence of decline of temperature. It is less easy 



more the extraordinary fact (familiar to all practical observers) of 

 birds of passage, unless when driven by stress of weather, returning, 

 both in summer and winter, to their former place of abode, and this 

 even when reared in confinement, and released immediately previous 

 to their first journey. — Ed. (See note to p. 31.) 



+ It is most difficult thus to generalize in the class of Birds. For 

 instance, the iSallinules, or Moorhens, — habitual swimmers, — have no 

 connecting membrane to the toes ; while the Terns, which are never 

 seen to swim, have their toes completely webbed, &c. Even the Herons, 



to imagine physical agency that should constantly impel migratory the Curlews, and numerous other lenders, will sometimes take the 

 rntmais to travel in the right directi n; and the marvel increases i water of their own accord, and swim across pools, though their stxuc 

 when we consider the length of route ordinarily traversed, au' 1 still ' ture does not indicate such a habit. — Ed. 



