THE YOUNG FAMILY. 321 



them until they are able to support the severities 

 of the weather uninjured, is still continued? 

 Among a large number of birds this is the case. 

 The little chick almost as much requires the fos- 

 tering heat of the parent's breast as did the egg 

 from which it has just emerged. In such cases it 

 is customary for the parent bird still to cover her 

 nest. The titmouse, our most constant orchard 

 companion, does so in an interesting manner. At 

 the expiration of a fortnight her young are all 

 hatched, but the mother still sits upon them 

 several times during the day, and probably also 

 during the night. This time is gradually short- 

 ened, so as to harden the constitutions of her tiny 

 offspring, upon the same principle as that on which 

 mothers of our own species cause their children to 

 leave off flannel clothing, by tearing a strip off 

 every day, until a mere rag is left, which is at last 

 committed to the flames. So the blue tit gradually 

 shortens the time during which she communicates 

 warmth to her young ones, until at length they are 

 sufficiently fledged not to require such protection. 

 It is said that a number of the smaller birds sit 

 upon their young during the night after they have 

 ceased to protect them during the day. 

 Y 



