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LOUISIANA HAWK. 



Falco Harrisii. 



PLATE CCCXCII. Female. 



The varying modes of flight exhibited by our diurnal birds of prey 

 have always been to me a subject of great interest, especially as by 

 means of them I have found myself enabled to distinguish one species 

 from another, to the farthest extent of my power of vision. On consi- 

 dering this matter, I have become fully convinced that a greater 

 length of the wings in any one species is not, as most naturalists have 

 imagined, an indication of its greater power of flight. Writers of the 

 present day who, judging of the flight of birds from such circumstances, 

 think that those species which have longer and, as they suppose, more 

 complete wings, fly with more rapidity than those whose wings are 

 comparatively short, are, in my opinion, quite mistaken. They judge 

 in this matter, not from experience, but from appearance, having pre- 

 viously determined theoretically that a long wing is a more efficient 

 instrument than a short one ; and being acquainted with birds only 

 through the medium of skins and feathers, presume to inform us as to 

 their comparative agility. The power of flight in birds of any kind 

 depends not upon the length, amplitude, or shape of the wings, but 

 upon the rapidity with which these members are moved, and the mus- 

 cular energy applied to them. It is not a little surprising to me that 

 not one of the authors who has written on this subject, has spoken of 

 the mode of flight of our Turkey Buzzard, which, notwithstanding its 

 very ample wings, is one of the very slowest birds ; for, although it 

 manages to rise to a great height, all its movements are laborious and 

 heavy, unless when it is at some considerable elevation. The ampli- 

 tude of its wings serves it in sailing only, never in enabling it to pass 

 swiftly through the air, as birds of much shorter wings, but greater 

 muscular energy, are wont to do. 



The Golden Eagle, which has universally been considered as a bird 

 of most extraordinary powers of flight, is in my estimation little more 

 than a sluggard, though its wings are long and ample. It is true that it 

 can sustain itself for a very considerable time on wing, but the observer 



