36 BRITISH BIEDS 



as merely due to a similar mode of life, and therefore to the develop- 

 ment of certain structures which are in direct relation to that mode 

 of life, how about the superficial likeness of the owls to the goat- 

 suckers, which is almost as well marked as to the hawks ? In 

 Australia and other parts of the East there are two genera of goat- 

 suckers which have received the names of Podargus and Batracho- 

 stomus. These birds are wonderfully like owls. They have the 

 same brown-and-grey and soft plumage ; their flight is equally noise- 

 less and, altogether, anyone who saw the living Cuvier's Podargus 

 recently on view at the Zoological Gardens might well be pardoned 

 for thinking it an owl. The fact is that we must be careful not to 

 be prejudiced in any direction. Superficial similarities may or may 

 not go with real likeness. Speaking generally, one should be disposed 

 to lay greatest stress upon characters which have no obvious relation 

 to mode of life as likely to be of the most use in indicating blood 

 relationship. It is easier, however, to lay down general principles 

 of this kind than to apply them to birds. As has been already 

 mentioned, birds are so uniform in anatomy that in such characters 

 as brain, lungs, and other internal organs which are not so directly 

 under the immediate influence of their surroundings, there is but 

 little difference. Such characters afford no help to the systematist. 

 We are obliged, therefore, to rely upon other and really less 

 important points. 



In most books upon ornithology in this one, for instance the 

 scheme of classification is set forth in the shape of a list beginning 

 with one particular group and ending with another. This is merely 

 due to the physical properties of sheets of paper. A linear scheme 

 is really an impossibility ; to represent classification properly we 

 want a solid diagram, showing how from a root-stock branches 

 arose and pushed their way in every direction. Another defect of 

 the linear scheme is that we must begin somewhere and end some- 

 where. In this book we begin with the Passeres and end with the 

 Parrots ; others start with the Accipitres, in spite of the protest of 

 Michelet against placing the cowardly, flat-headed, stupid hawks at 

 the summit of bird creation. It doesn't matter where we begin or 

 where we end as long as w r e carefully bear in mind that a linear 

 classification is only a convenient way of briefly stating certain 

 facts, and that it does not pretend to be a copy of Nature. An 

 alternative method of expressing the facts of structure in space of 

 two dimensions is the Stammbaum, originally made in German \ ; 

 but this inevitable tree of life is open to the serious objection of 



