CLASS II. AVES 



and frequently only acquire their mature dress after the lapse of three or four years, the plumage 

 undergoing a certain change at each moult. These circumstances undoubtedly throw great diffi- 

 culties in the way of the student of ornithology, and it is perhaps not nuich to be wondered at, if 

 we have sometimes half a dozen different names for different states of the same species ; but it 

 must also be confessed, that in this, as in other departments of natural history, the desire to de- 

 scribe new species has often led to an unjustifiable multiplication of errors of this description. 



In a zoological point of view the greatest importance attaches to the feathers of the wings and 

 tail, to which different names have been given. The quills are inserted into all the bones of the 

 wing, but the longest are those attached to the bones of the hand, and to these the name of pri- 

 maries is given. The feathers supported by the fore-arm are denominated secondaries, and those 



attached to the humerus tertiaries. The thumb 

 also bears a few quills, which form what is called 

 the alula, or bastard wing. These, and some 

 other feathers to which particular names have 

 been given, are shown in the annexed engrav- 

 ing. The base of the quills is covered by a se- 

 ries of large feathers called the ^ving coverts, 

 which are also distinguished into ^^r/raary and 

 secondary. The feathers of the tail are fur- 

 nished with numerous muscles, by Avhich they 

 can be spread out and folded up like a fan. 

 Their bases are also covered both above and 

 beneath by smaller feathers, which arc called 

 the tail coverts. 



It is impossible to conceive any covering more 

 beautifully adapted to the peculiar wants of 

 these creatures than that with which they are 

 endowed by nature. All the feathers being di- 

 rected backward, the most rapid motion through 

 the air only tends to press them more closely 

 to the body, and the warm air, confined among 

 the inner downy fibers, is thus effectually pre- 

 vented from escaping. In the aquatic birds the 

 feathers are constantly lubricated by an oily se- 

 cretion, which completely excludes the water. 

 In the wings the quill-feathers exhibit in the 

 highest degree a union of the two qualities of 

 lightness and strength, while by their arrange- 

 ment they can be folded togethe" into a very small compass. 



In their reproduction birds are strictly oviparous. The eggs are always inclosed in a hard 

 shell, consisting of calcareous matter, and, unlike the animals of some of the succeeding classes, 

 birds, instead of abandoning the hatching of their eggs and the development of their offspring to 

 chance, almost invariably devote their whole attention, during the breeding season, to this im- 

 portant object, sitting constantly upon the eggs to communicate to them the degree of warmth 

 necessary for the evolution of the embryo, and attending to the wants of their newly-hatched 

 young, until the latter are in a condition to shift for themselves. 



Most birds live in pairs during the breeding season, which usually occurs only once in the year; 

 in many cases the conjugal union is for life. Both sexes generally take an equal part in the care 

 of the young. They usually form a nest of some description for the reception of the eggs ; this 

 is composed of the most diverse materials, such as sticks, moss, wool, vegetable fibers, &c. ; in 

 many instances the work of these little architects must excite the admiration of every observer. 

 The nests of different individuals of the same species arc generally not only of the same form, but 

 even composed nearly of the same materials, so that a person, accustomed to the inspection of 



A, ear coverts ; B. bastard wing; C D E, wing coverts ; F, prima- 

 ries; G, scapulars; H, secondaries; L, tail coverts; K, under 

 tail coverts, not shown. 



