MOTIONS OF OTHER ANIMALS. 361 



the honey of flowers. The vibratory motion of the 

 wings in these instances is only to buoy them up so 

 as to retain their place ; but the instant they are 

 alarmed by the approach of danger, they may be 

 seen to take several long strokes with their wings, 

 and dart off with the rapidity of lightning. This is 

 well illustrated by the motions of birds preparatory 

 to flight, as they may be observed always to take se- 

 veral deep inspirations, at the same time often rising on 

 tiptoe, and pufiing out and balancing their bodies to 

 feel whether they have thrown enough air into their 

 bones and feathers to float them along. Birds of prey 

 {RaptoreSy Vigors) seem to have the greatest power 

 both of fllling their bodies with air and of expelling it 

 again at pleasure. Hence the kestril (Falco tinnun- 

 culus) may be seen floating about for a considerable 

 time without moving a wing, or perhaps drawing a 

 breath, till it can hold out no longer, when it flutters its 

 wings rapidly, not for moving to a difterent place, for 

 it remains stationary, but to recover its decreasing 

 buoyancy by inhaling a fresh supply of air. For the 

 same reason a trout will oscillate its body when losing 

 ground by the rapidity of a stream. The osprey {Falco 

 ossifragus), on the other hand, we have seen, at the 

 Kyles of Bute and elsewhere, shoot down like a thun- 

 derbolt from the air into the sea, plunging far into the 

 water upon a fish she had marked for her prey,* — a 

 movement only to be explained by the rapid expulsion 

 of the air which had been the chief agent in keeping her 

 previously afloat in the region of the clouds. Many 

 birds which prey on smaller game have somewhat simi- 

 lar methods of poising and balancing their bodies, of 

 which the water-ouzel ( Cinclus aquaticus, Bechstein) 



* 'Super est Haliaetos,' says Pliny, ' clarissima oculorum 

 aeie, librans ex alto sese, visoque in mari pisce, pra^ccps in sum 

 ruens, et diseussls aquis, rapiens.' — Hist. SS^at. 



VOL. vr. 31 



