12 



Curassows especially, feeding occasionally upon small mammals or 

 birds. The Curassows at the Zoological Gardens will catch and 

 kill and eat a mouse in almost as systematic a manner as the 

 Kestrel does, and the same may be said of many allied forms. It 

 is quite conceivable that, under changed conditions of their normal 

 surroundings, the Curassows might be compelled to subsist entirely 

 on small mammals or on birds of their own catching ; and in this 

 case such of their descendants as developed characteristics better 

 fitting them for their raptorial mode of life would be more likely 

 to survive and to leave numerous descendants than the birds that 

 did not vary in that direction from the parental form. 



The case of the Curassows is especially interesting because in 

 many of their structural characteristics they closely approach some 

 of the aberrant Aetomorphs — the Polyborines and the allied forms, 

 for example. Then again, there is the case of the well-kno^vn 

 Carnivorous Parrot, Avhich has made quite a new start in life 

 within the last fifty years, and given up a diet of fern-roots for a 

 more substantial one of mutton. Xo one can for a moment doubt 

 that if its former diet failed, this particular form of Parrot could 

 soon pick up a living by preying upon other denizens of that part 

 of the world ; and even if deprived of sheep-flesh it could supply 

 its needs just as adroitly by attacking other animals as it does now 

 with the colonists' sheep. In course of time, unless external 

 circumstances intervened to prevent it, natural selection would 

 develope a bird that might still retain some of the internal 

 structural characteristics of the parrots, and yet be, externally, and 

 in all essential points in its habits, a veritable Bird of Prey. No 

 one, again, who will study the appearance and the habits of the 

 remarkable Cuvier's Podargus, now (1885) living in the Zoological 

 Gardens, can doubt that this very owl-like bird represents either 

 one of two things : it is either a comparatively-unmodified 

 descendant of the common ancestors of the Owls and the Goat- 

 suckers, or else it is a raptorial type developed from a Goat- 

 sucker stock. Similar observations apply also to birds like the 

 Skuas, Albatrosses, Storks, and other birds that stand close upon 

 one part or another of the Aetomorphse as at present recognized. 

 Bearing these facts in mind, and taking into account the sum 



