1 82 Summer Studies of Birds and Books CHAP. 



subject the moult. Before we go on to glance at 

 Aristotle's accounts of species, let us see whether he 

 has anything to tell of this. It is not, of course, to be 

 expected that we should find him explaining, as 

 the modern ornithologist does or ought to do, the 

 variations of plumage assumed by birds at different 

 seasons of the year, or at different stages of their 

 existence ; nor does he seem to recognise the moult 

 as a universal law of bird-life. To get so far as this, 

 he would have needed to give his life to ornithology 

 alone, instead of to all the sciences then known to man. 

 Yet he does seem to know that some birds change 

 their plumage at regular times. In the third 

 book of his Natural History he writes : " Birds do 

 not change their colour by age, except the Crane, 

 which becomes darker. But from the change of 

 season, as when it becomes cold, some of those 

 which are of one colour only, black or gray or brown, 

 become white, as the Eaven, the Sparrow, and the 

 Swallows ; but of those which are white none have 

 been noticed becoming black. And, according to the 

 seasons, many birds change their colours, so that 

 they fail to be recognised except by an expert. " J 

 In spite of the strange statements which this passage 

 contains, the last sentence is as true as it can be. 

 Once or twice he alludes to a seasonal change of 

 colour as a well-known fact in some particular 



1 H. A. iii. 12. 



