BIRDS' NESTS. 139 



who, attentive as they are under ordinary cir- 

 cumstances to the wants of their own brood, 

 take no further notice of those who have been 

 turned out of doors by the selfish intruder, 

 but suffer them to perish of want. Indeed 

 the appetite of the young cuckoo is so voracious, 

 that it would be next to impossible for any 

 single pair of birds to supply any more than 

 his need and their own. This extraordinary 

 voracity appears to be owing, in some mea- 

 sure, to the disproportionate size of the egg 

 and adult bird, which makes it necessary that 

 the nestling should grow very fast in order to 

 obtain maturity in time to migrate in Sep- 

 tember, the period at which the young bird 

 disappears. 



How wonderful must be the instinct im- 

 planted in a bird which, reared by foster- 

 parents (themselves spending their whole lives 

 in the same country), and never having been 

 taught by example or the society of its fellows, 

 wings its way across the sea, an element of 



