52 THE FLIGHT OF BIRDS 



lightest to the heaviest, we should at the same time 

 be arranging them according to their angles of ascent 

 — the angle which each makes with the horizon when 

 the line of his ascent is as near to the vertical as his 

 build and his powers allow. In the case of all very 

 big, bulky birds, I believe the wing rotates reluctantly 

 and with difficulty at the shoulder. The Gannet, 

 Pelican, Cormorant, Eagle I have tested, and found 

 that they have very little power of lowering the front 

 edge of the wing relatively to the back ; one Eagle 

 was a partial exception. I have never had a live or 

 a freshly-killed Condor at my disposal, but there is 

 reason to believe that the Condor is among the 

 stiffest of the stiff. The way in which Condors are 

 trapped in Chile — it is described by Darwin in his 

 Journal of Researches (Chap, ix) — supplies indirect 

 evidence of the great bird's limitations. The plan 

 is to place a carcass "ona level piece of ground 

 within an enclosure of sticks with an opening, and, 

 when the Condors are gorged, to gallop up on horse- 

 back to the entrance, and thus enclose them : for 

 when this bird has not space to run it cannot give 

 its body sufficient momentum to rise from the 

 ground." In fact a Condor cannot rotate his wings 

 and set them as they must be set if his line of 

 ascent is to make a large angle with the horizon. 

 As far as I know, all birds of great bulk have this 

 defect, but when we come to birds of medium size we 

 find great variations, and it soon becomes apparent 

 that it is largely a question of habitat and environ- 

 ment. The Pheasant and Duck — I have tested the 

 Mallard, the Sheld-duck and the Teal as representa- 

 tive of the Ducks — have great freedom of movement 



