52 THE FLIGHT OF BIRDS 
lightest to the heaviestygve should at the same time 
be arranging them scold 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. 1x)—supplies indirect 
evidence of the great bird’s limitations. The plan 
is to place a carcass “on a 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 
