328 THE LIFE OF A BIRD. 



yellow-warbler. As this species was taken as a 

 symbol of friendship, it proved unfortunately that 

 true friendship was even more rare than Audubon 

 thought. The mistake of an ornithologist so 

 familiar with the character and habits of birds as 

 Audubon was, teaches humility to us, and incul- 

 cates kindly judgment in regarding the failures of 

 others. Such mistakes are by no means uncom- 

 mon at an earlier period of the bird's history than 

 that at which the bird in question was discovered. 

 And we are reminded in this respect of the mis- 

 takes constantly committed by entomologists in 

 the natural history of the spiders, the young of a 

 well-known species being frequently mistaken for 

 an adult of some new species. It is a well-known 

 fact that the plumage of birds changes several 

 times before it attains that state which character- 

 ises the adult bird. The time required for this 

 varies from one to five years, so that, as in the 

 instance just quoted, some birds may even rear a 

 progeny before they acquire the same plumage as 

 adult birds. This explains and apologizes for 

 Audubons mistake. 



It has already been said that the young bird 

 appears, soon after its exclusion from the shell, 



