BIRDS ORGANIZATION DIAGRAM 4 



61 



enveloped in a sort of very slender skin, which forms two 

 ligaments, floating in the albumen towards the two ends of the 

 egg. We can also see, towards one end of the egg, a place 

 where the albumen does not touch the shell, and which is full of 

 air ; and this is called the air-sac. 



It is necessary for eggs to be kept at a raised temperature for 

 some time, in order to produce chickens. In this country, the 

 mother hatches the eggs by sitting on them, scarcely moving 

 from them at all, until the young ones are hatched. These 

 break the shell by pecking at it with their beaks ; and still 

 require to be brooded over by their mother for some time ; and 

 they live under her until they are grown large. The heat and 

 care of the mother are not however indispensable to rear fowls, 

 and they can be hatched artificially by means of an arrangement 

 called a hatching oven, where the temperature is kept nearly 

 equal, and sufficiently high to develop the chick. With some 

 precautions, young chickens can thus be very easily reared. 



Birds generally build nests for breeding, which are sometimes 

 true masterpeices of architecture. Some are solidly built of 

 earth, others made of twigs ; there are 



\ $[&? \ f jftc'fi t some which float on the water ; and we 

 shall mention under each species any- 

 thing which is interesting about its nest. 

 But it ought to be thoroughly com- 

 prehended that no nests ought ever to be 

 destroyed, except those of birds of prey 

 such as falcons or hawks. All other 

 nests ought to be respected. All young 

 birds on coining out of the egg without 

 exception eat insects, and nothing but 

 insects. Even those species which de- 

 stroy corn, always feed their young with 

 Reed Warbler. caterpillars, grubs, and all the creatures 

 which are most mischievous to agriculture. All who have seen 

 young birds in the nest know what an appetite they have 



