278 ORNITHOLOGY. 



Birds are oviparous; in other words, are produced from eggs 

 consisting of a living point attached to a globular sac of nutri 

 ment called the yelk, surrounded by a layer of albumen, the 

 glair or white part, and enclosed in two series of membrane and 

 a hard calcareous shell. The egg is developed into a living, ac 

 tive chick, by the warmth which the parent supplies while sitting 

 upon the nest wherein the eggs are deposited ; or it may be 

 hatched in a breeding machine, by means of artificial heat of 

 about 96o Fahrenheit. The instinct of birds is wonderfully ex 

 hibited in constructing and locating their nests as places of com 

 fort and concealment, and in the exquisite workmanship displayed 

 in some of them. 



The process of incubation lasts a few weeks, when the young 

 is ready for exclusion. By means of a horny pointed scale at 

 tached temporarily to the tip of its beak, it succeeds in breaking 

 the egg-shell and forcing its way to freedom. &quot;At the end of 

 the second day, the first moving of the heart is perceptible, and 

 on the fifth, the whole frame of the little creature can be dis 

 tinctly seen in motion. The feathers make their appearance in 

 a fortnight. At the commencement of the fifteenth day, the 

 chicken begins to breathe, and on the nineteenth it is able to 

 peep.&quot; The gallinaceous and swimming birds can run about 

 and pick up their own food as soon as they escape from the egg ; 

 but more commonly the young are, for several days, unable to 

 quit the nest, and as is well known, are anxiously fed and cared 

 for by the parent birds. 



Few things have attracted more attention than the migration 

 of birds. The immediate cause of this is doubtless to be traced 

 to temperature and to food, particularly that which is adapted to the 

 sustenance of the young ; and the instinct of the bird accord 

 ingly leads it from one climate to another. 



The change of plumage, termed moulting, takes place in all 

 birds at least once a year, and sometimes oftener. Apart from 

 the ailment connected with this change, birds are subject to very 

 few diseases. In all countries they are said to be more long 

 lived than the quadrupeds of the same climate. 



Fowls sometimes live 20 years. Linnets and other little birds shut 



Pigeons, longer. up in cages often live 15 years. 



Canaries, 25 years. Robins, 17 do. 



Parrots, 30 do. Eagles, over 100 do. 



Pelicans, 80 do. Cockatoos, reach 120 do. 



Geese, 80 or 90 do. Swans, from 300 to 360 do. 



The fossil remains of birds, though not numerous, are entitled 



