76 EAGLES AND HAWKS 



survival of an ancestral coloration, but why it should have survived 

 alone in the osprey is at present, and probably always will be, 

 inexplicable. 



Why, in some, as in some Owls, the female should be so much 

 larger than the male, seems as incapable of explanation as the sexual 

 differences of coloration which many display. Perchance a closer 

 study of the habits of the few species yet left to us may afford a clue 

 to these riddles. 



In discussing the Accipitres, it has become a common practice 

 to begin with the Harriers : and this because, on account of the 

 curious, though imperfect, facial disc, they were supposed to form 

 the connecting link between the Owls or nocturnal birds, and the 

 Accipitres, or diurnal birds of prey. We now know that there was 

 no foundation in fact for this association. Others, it may be re- 

 marked, regarded the osprey as affording the connecting link because 

 of its reversible hind toe, and the absence of an aftershaft. Later 

 observations showed that this, also, was an association unjustified by 

 an appeal to anatomy. It is clear then that the resemblances 

 between Owls and Hawks are due to convergence, and not to 

 parallelism that is to say, they are not derived from a common 

 ancestry. We have reverted, in the treatment of the several types of 

 Accipitres dealt with in these pages, to the order adopted by the 

 older ornithologists in placing the Eagles first. But this, be it noted, 

 is not for systematic reasons, but because, owing to the brilliant 

 memoir of Mr. H. B. Macpherson on the Golden-Eagle, 1 we have 

 now a standard of comparison of the habits of the Accipitres during 

 the most critical period in their life-history. This is incomparably 

 the best of its kind which has yet been written. What follows 

 will serve more than anything else to show up the paucity of our 

 knowledge of all the rest of the Accipitres, and will stimulate, it is 

 to be hoped, some of the readers of this work to strive to fill up 

 these yawning gaps. A study of the sparrow-hawk on the lines laid 



1 H. B. Macpherson, The Home Life of a Golden-Eagle. 



