436 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1911. 
doubt have revealed the wings as fully extended as in figure 2.1 
Here the wings are just beginning to feel the weight of what they are 
to support and are commencing their first downward beat. And 
now, though it has orily traveled a few inches from the rock and the 
_feet have not yet been tucked away under the tail, the gannet is 
fairly on the wing, exasperatingly able and wishful to go beyond the 
range of our lens or even of our observation. 
II.—STEERING, SLOWING-UP, AND TURNING. 
The old idea that the wings of a bird simply flap up and down, and 
that by some means the body travels steadily along on a level hori- 
zontal course, has long been dispensed with. It is, however, difficult 
to realize, but none the less true, that at each full wing beat the body 
is raised as well as propelled. Perhaps this can be more readily 
appreciated by reference to a photograph, such as that represented 
in plate 3, figure 2. By good fortune the two gannets shown there so 
near together exhibit the two extremes of the positions which these 
birds ordinarily assume in flight. In the top left-hand bird the wings 
are raised and the body seems to be dependent from them, while in 
the lower bird the wings are far depressed and the body appears 
_ pushed up and supported by them; and this is precisely its position. 
The wings in their rapid descent found resistance in the air, and as 
soon as this resistance exceeded the force of gravity acting on the 
bird the body was elevated at the same time that it was driven 
forward, only, of course, to sink once again on the wings being raised. 
Thus the path of a flying bird is a succession of ups and downs, but 
the movements of the wings being so very much greater in extent 
cloak those of the body, and so gracefully and smoothly are the 
actions performed that we do not realize the undulatory nature of 
the course. The attitude of the right-hand top bird, a kittiwake, in 
the same photograph (pl. 3, fig. 2), is interesting, as it shows the bird 
steering by the aid of its feet. The very extensive use some birds 
make of their feet during flight requires consideration. Not only are 
they freely used for steering, but they are also often employed as 
brakes to lessen speed, much in the same way as a drag is used to take 
way off an incoming vessel. In plate 4, figure 1, the immature 
gannet there depicted is trailing its partly expanded and lowered 
feet, thereby causing considerable resistance to its forward progress. 
To birds which quarter the surface of the ocean for a livelihood, feet 
have yet another use during flight. As the bird swoops downward to 
snatch its swimming prey the legs are dropped, and the moment the 
quarry has been seized, if not before, the feet are plied vigorously to 
run along the surface of the water and thus not only act as buffers and 
1 The tip of the left wing of the bird in this figure has been retouched, as owing to an accident a portion of 
the photograph (involving about half of the primaries) had become obliterated. The other photographs 
have not been retouched in any way and have been chosen to illustrate the various points discussed rather 
than because they were good photographs. 
