108 AGE OF BIRDS. 



outside as near the colour as possible of the branch 

 which supports them. The nest of the long-tailed 

 tit is shaped like an egg, and has only a very small 

 opening at the top; over this the bird fixes a feather 

 in a slanting direction, so as to carry off the rain ; 

 and if the finger is passed into the mouth of the 

 nest, several feathers are found placed crosswise as 

 an additional protection. 



When the nests of birds are undisturbed, and 

 they have laid the usual number of eggs, which 

 varies in different species, the female begins to sit. 

 The constancy with which this sitting, or incuba- 

 tion, is continued, is a beautiful illustration of the 

 instinct of animals. If the mother-bird were to 

 absent herself for a few hours, and leave her eggs 

 exposed to the cold, the young ones contained in 

 them would be destroyed. This fact she has been 

 taught by God ; and, contrary to all her usual 

 habits, she remains day after day, very rarely stir- 

 ring ; and in some instances she sits so closely, 

 that she requires feeding by her mate. We have, 

 indeed, known examples in which the white- 

 throated wren, thougn a very shy and timid bird, 

 has suffered herself to be taken by the hand, rather 

 than abandon her eggs. The length of time re- 

 quired for hatching differs in different species. 

 The common fowl hatches in about twenty -one 

 days. 



Some birds live to a great age. The eagle and 

 the parrot will live, under favourable circumstances, 

 a hundred years. The swan is said to live two or 



