150 ACCIPITRES. 



animals which are the chief prey of the owls : the kestrel, 

 which is usually classed with the falcons, hawks for beetles 

 and large moths after sunset ; and the osprey, and the sea- 

 eagle (when it fishes) are constrained either to fish in the 

 twilight, or, at some seasons, to fare but scantily ; and though 

 they, more especially the latter, can endure hunger for a long 

 time, they at all times prefer food to fasting, if food can be 

 obtained. The eye of the buzzard is protected from side- 

 lights by the concha of feathers round the eye, in order that 

 these may not interfere with and confine the fainter light 

 which comes from those shady places in which the prey is 

 found, just in the same manner that the projecting upper part 

 of the orbit in the sky-hunting birds protects their vision 

 from the direct rays of the sun, and enables them to see 

 better below them. The eyebrow in man answers a similar 

 purpose ; and, indeed, there is no animal which hunts in the 

 clear light of the sun, in which the eye is not more or less 

 defended by some such contrivance. The sea-eagle, again, 

 can bring over the eye a peculiar membrane, which acts as a 

 sort of curtain, in excluding the level light of the twilight 

 sky, and allowing the full power of the organ to the dimmer 

 light from below ; and that instrument of twilight vision was 

 regarded by Aristotle as a means of blindness. He is not to 

 be blamed, or even wondered at, because the principles of 

 optics were little known in his time ; but those moderns who 

 have repeated the assertion, are not so excusable. 



The nocturnal birds of prey have the eye with a more ample 

 and complete concha, and also the iris much more susceptible 

 of motion than the day-birds so much so, indeed, that a 

 strong light appears to shut the pupil altogether, and the 

 bird becomes bewildered, and cannot see its way. The sen- 

 sibility will abate, however, under circumstances which render 

 such an abatement necessary to the comfort of the bird. 

 There have been instances of tamed owls (and owls are easily 



