Vlll INTKODtrCTION. 



birds, in some instances by cutting up recognized genera, and in 

 others by uniting several together, I can only plead that I have 

 not done so capriciously, but in order to facilitate the perception of 

 the community of origin, -which must more and more interest those 

 who accept the theory of evolution. 



It has been accepted as an axiom amongst ornithologists that 

 genera must be founded upon structural characters. The reader 

 ■will find that in the first division of my work I have made use of 

 characters that are not structural in defining some genera, and 

 have, in many cases, considered so-called structural characters as 

 having only value enough to divide genera into subgeneric groups. 

 In the second division of my work I have convinced myself that 

 these so-called structural characters have no generic value at all, 

 and I have been obliged to fall back upon colour or pattern of 

 colour as the only character which indicates near relationship. In 

 my opinion the pattern of the colour in the family or subfamily of 

 Turdinaj is a character which is more trustworthy (as showing com- 

 munity of origin), which in fact dates further back than the shape 

 of the wings, tail, or biU. 



The species included in this volume are admitted by most modern 

 ornithologists to be the most highly developed group of birds. 

 Amongst them are found the finest songsters, showing the highest 

 development of the vocal organs, whilst few families can rival them 

 in their powers of flight. In many species their range of migra- 

 tion extends from beyond the limit of forest-growth in the Arctic 

 regions to the limit of continental land in the Southern hemisphere. 

 It is difficult to say which of the two subfamilies is most highly 

 developed. The Sylviinae have acquired a complete double moult, 

 and have most of them lost the spotted plumage of their remote 

 common ancestors, not only in the adult but also in the young ; but 

 they still rctahi the scutcllated tarsus. The Turdinas, on the other 

 hand, have scarcely the rudiments of a spring moult, and retain 

 the spotted plumage of their remote common ancestors in the nestling 

 plumage, but the scutellated tarsus only occasionally appears in the 

 Tery young birds of a few species. On the whole, however, I am 

 inclined to give the palm to th.e latter group. They are un- 

 doubtedly the finest songsters. It may be that their greater size 

 and strength has rendered the other changes less necessary. They 



