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. This is the reason why these birds when they
fly make use of their legs as a tail, stretching them out behind,
and so rendering them serviceable, whereas in any other position
they would be simply an impediment.
In other birds, where the legs are short, these are held close
against the belly during flight. In some cases this is merely to
keep the feet out of the way, but in birds that have talons the
position has a further purpose, being the one best suited for
rapine. Birds that have a long and a thick neck keep it stretched
out during flight; but those whose neck though long is slender fly
with it coiled up. For in this position it is protected, and less
likely to get broken, should the bird fly against any obstacle.
In all birds there is an ischium, but so placed and of such length
that it would scarcely be taken for an ischium, but rather for a
second thigh-bone; for it extends as far as to the middle of the
belly. The reason for this is that the bird is a biped, and yet is
unable to stand erect. For if its ischium extended but a short way
from the fundament, and then immediately came the leg, as is the
case in man and in quadrupeds, the bird would be unable to stand up at
all. For while man stands erect, and while quadrupeds have their heavy
bodies propped up in front by the forelegs, birds can neither stand
erect owing to their dwarf-like shape, nor have anterior legs to
prop them up, these legs being replaced by wings
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