There has lately been some discussion about the hovering of kestrels: the point being whether the bird can or cannot support itself in the air while stationary, without the assistance of one or more currents of air. The kestrel is the commonest hawk in the southern parts of England, so that many opportunities occur to observe his habits; and there ought not to be any doubt in the matter. It is even alleged that it will go far to decide the question of the possibility of flight or of the construction of an aerial machine. Without entering into this portion of the discussion, let us examine the kestrel's habits. This hawk has a light easy flight, usually maintaining an altitude a little lower than the tallest elms, but higher than most trees. He will keep this particular altitude for hours together, and sweep over miles of country, with only occasional variations--excluding, of course, descents for the purpose of taking mice. It is usually at this height that a kestrel hovers, though he is capable of doing it a much greater elevation. As he comes gliding through the atmosphere, suddenly he shoots up a little (say, roughly, two or three feet), and then stops short. His tail, which is broader than it looks, is bent slightly downwards; his wings beat the air, at the first glance, just as if he was progressing. Sometimes he seems to oscillate to one side, sometimes to the other; but these side movements do not amount to any appreciable change of position. If there be little or no wind (note this) he remains beating the air, to the eye at least perfectly stationary, perhaps as much as half a minute or more. He then seems to slip forward about half a yard, as if a pent-up force was released, but immediately recovers himself and hovers again. This alternate hovering and slipping forward may be repeated two or three times: it seems to depend on the bird's judgment as to the chance of prey. If he does not think a mouse is to be had, at the first slip he allows himself to proceed. If the spot be likely, or (what is still more tempting) if it is near a place where he has taken prey previously, he will slip and bring up several times. Now and then he will even fetch a half-circle when his balance or impetus (or both) is quite exhausted, and to return to the same spot and recommence. But this is not often, as a rule, after two or three slips he proceeds on his voyage. He will repeat the same round day after day, if undisturbed, and, if the place be at all infested with mice, he will come to it three or four times a day. There is, therefore, every chance of watching him, if you have once found his route. Should he spy a mouse, down he comes, quick but steady, and very nearly straight upon it. But kestrels do not always descend upon prey actually in view. Unless I am much mistaken, they now and then descend in a likely spot and watch like a cat for a minute or two for mice or beetles. For rest they always seek a tree.