. Animal flight; a record of observation . 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 th
. Animal flight; a record of observation . 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 Fig. 4. 10th Jan., Jharna Nullah.—Vultureleelooping in a strong wind. Fig. 5. 8th Jan., 1911, Jharna Nullah.—Scavenger leelooping. This was thefirst scavenger seen up. Cloud was getting thinner, and soarability wasincreasing. Previously cheels only had been circling. Note diminutionof speed all round the loop. Track marked at i sec. intervals. ANIMAL FLIGHT. 37 Referring to fig. 5, it will be noticed that there isa somewhat sudden increase of speed immediately afterthe loop and at the commencement of the leewardglide. I have been able to observe the adjustment ofthe wings used to initiate this increase of speed, andshall describe it in a later chapter. The length of theleeward glide may, in some cases, amount to 100 metresor more. We have now completed our preliminary descrip-tion of circling. In this form of flight, as will be shownlater, speed is relatively low, and, as has been stated,there is frequently a gain of height. We have now tomake a preliminary description of another
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