428 THE EMPIRE OE THE AIR. 



sorts of ways. Their wings were clipped short : their wing's were h^ngtli- 

 ened out. Tliey were made semi-long, narrow and long, narrow and 

 short. They were pieced out with i)rimary feathers from birds of prey, 

 thoroughly fastened on Mith glue, and pressed on in the vise. 



This is Avhat happens when a bird's wings are altered; when the 

 active surfaces are changed in extent and form, the creature being- 

 accustomed to a particular mode of flight starts off in his habitual man- 

 ner; but his organs are no longer adapted to produce their customary 

 effects, they are shaped to i^roduce different effects. Thus the bird 

 finds itself with habitudes and instincts for one mode of flight, and 

 with a new arrangement of feathers adapted to another mode. The 

 latter constantly impresses liim with the necessities of the moment, 

 and these necessities com]>el him, willy-nilly, to fly as flies the other 

 type of bird wliich has been forced upon him. 



Thus, a kestrel falcon, a good soarer, who had his nest near my 

 observatory, has just one-half in length of liis primary feathers cut oft'; 

 the result was forcibly to transform him into a rowing bird. I restored 

 him to liberty, and as he remained on his hunting ground, I had every 

 opportunity to observe him. Although nuich hampered the bird was 

 not very unhappy, the prey sometimes escaped, but he made up for 

 what he had lost by increased activity. He was easily singled out, for 

 the mutilation gave him an unusual figure; his long tail seeming longer, 

 now that it was not accompanied with two long wings, and it attracted 

 attention from afar. And so he had to row constantly. Once in a 

 while he would try gliding in the old fashion, but as he found himself 

 dropping too rapidly, the instinct of necessity for support compelled 

 him again to beat the air. 



1 have transformed kites into stormy petrels by clipping off' half the 

 width of the wing for its whole length, and abolishing the tail. The 

 result was to comiDel them, notwithstanding tlieir habits of soaring 

 upon light winds, to await instead the brisk winds which alone could 

 sustain them without fatigue. 



As will be seen, to succeed in such observations we must absolutely 

 control the bird and have him at command. Experiments withincreased 

 surfaces did not succeed as well; I tried them on pigeons, and on two 

 kites who were old neighbors of mine. I only succeeded in jn-oducing 

 birds which were exceedingly awkward in their movements. I ought 

 to have practised u])on a goss-hawk, but how couhl I have afterwards 

 obser^•ed such a mere lurd of passage, whereas the kites a have fixed 

 habitat, they are well recognized, so that if there is an important 

 feather missing iu one of the kites in your neighborhood, you can 



recognize liini, single him out, and consequently observe him. 



* * # # * * * 



The Hawl- type. — These are here separated from the great family of 

 birds of prey, because, although they are raptores, there are between 



