. Animal flight; a record of observation . iffer-ence between the speeds shown on the leeward andwindward sides of the circle. It is probable that it isa case of ease-circling, that is to say, circling withoutattempt to gainheight. The windwas very light, justenough to moveleaves, when thisrecord was taken. In the pres-ence of a slightlystronger wind thecircles may overlapby a greater dis-tance, as shown in f Ifig. 3. In certain /cases, especially in Jthe presence of a \.strong wind, the Fig. 2. intervals between Track of cheel ease-circling in light wind. Time* marks at i sec. intervals. the
. Animal flight; a record of observation . iffer-ence between the speeds shown on the leeward andwindward sides of the circle. It is probable that it isa case of ease-circling, that is to say, circling withoutattempt to gainheight. The windwas very light, justenough to moveleaves, when thisrecord was taken. In the pres-ence of a slightlystronger wind thecircles may overlapby a greater dis-tance, as shown in f Ifig. 3. In certain /cases, especially in Jthe presence of a \.strong wind, the Fig. 2. intervals between Track of cheel ease-circling in light wind. Time* marks at i sec. intervals. the loops may be still greater. I propose the term leeward looping or<: leelooping to describe this latter form of flight. Asshown in fig. 4, the diminution of speed indicating gainof height may occur chiefly at the point marked A, thepoint where the bird has turned round to face thewind. In some cases in leelooping, when observed atsome distance from the side, there appears at this pointto be a vertical gain of height of as much as 1 or z. ANIMAL FLIGHT. 35 metres. In some cases in leelooping the bird appearsto gain height during the whole of the loop. That isto say, it gains height not only while facing the wind,,but also 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 tof
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectan, booksubjectflight
