. Animal flight; a record of observation . lso when going with the wind ; in short, during the whole time that it ison a curved course. Such acase is illustrated in fig. It might be thoughtthat the difference be-tween circling and lee-looping depends merely onthe presence or absence ofwind. I doubt whetherthis is the case. For in-stance, the case of leeloop-ing illustrated in fig. 5was recorded in a lightwind just strong enoughto move leaves. I have onone occasion seen circlingwith scarcely perceptibledrift to leeward in astrong, stormy Fig. 3. 8th Jan., , Jharna Nullah.—Thin c
. Animal flight; a record of observation . lso when going with the wind ; in short, during the whole time that it ison a curved course. Such acase is illustrated in fig. It might be thoughtthat the difference be-tween circling and lee-looping depends merely onthe presence or absence ofwind. I doubt whetherthis is the case. For in-stance, the case of leeloop-ing illustrated in fig. 5was recorded in a lightwind just strong enoughto move leaves. I have onone occasion seen circlingwith scarcely perceptibledrift to leeward in astrong, stormy Fig. 3. 8th Jan., , Jharna Nullah.—Thin cloud. Glare. Cheels hadstarted at No other speciesof birds up. Cheel circling markedat h sec. intervals. There can be no doubt that the amount of leewarddrift in circling differs at different times, owing tofactors not yet understood. I may quote the followingdiary extracts bearing on this matter : July 14th, 1910. At —Two cheels seen circling together. Onechanged its movement from circling to leelooping. Shortly afterwards. 36 ANIMAL FLIGHT. the other made a similar change. A minute later both birds glided downand settled. Widespread soaring began at September 29th, 1910. At —An east wind, somewhat strong,moving branches. Sunshine. Isolated small cumulus clouds. Scantyclouds of higher layer. Four vultures seen circling in and out of thebase of a small cumulus cloud at a height of 1,100 metres. Their leewarddrift was not so much as that of the cloud. In a few minutes they werecircling nearly overhead, and the cloud was far awayto leeward. I made no record of the size of this cloud,but my recollection is that it was not larger in anydimension than eight or ten times the span of a vul-ture. Cheels and vultures were circling and flex-gliding to windward. They were leelooping whengoing to leeward.
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