SIDE IvIGHTS ON BIRDS 



itself, and must, therefore, have been several 

 miles high, while the nearest must have been quite 

 a mile above the earth's surface. 



Gatke's belief that the height of normal mi- 

 gration is at least 20,000 feet has not been found 

 to hold good. It has been estimated by the 

 most competent observers that wagtails fly about 

 150 feet from the sea, swallows between 40 and 

 100 ft. and meadow pipits as low as 20 feet, whilst 

 sandpipers, plovers, ducks and other high-flying 

 birds rarely exceed 8,000 feet. 



In order to secure further data Col. Meinertz- 

 hagen advertised in the " Times," requesting 

 pilots in the Royal Air Force who have special 

 means of registering elevation to provide him 

 with their estimates. One of the replies was as 

 follows : — 



" On April ist., I was surprised to meet 40 

 cock ostriches at 17,000 feet. I attacked them 

 at once and broke up their formation. One nose- 

 dived on to the General's tent, whilst another 

 crashed into our cook-house." 



But apart from the inevitable hmnorist many 

 useful details were supplied by saner corres- 

 pondents. Rooks were noted at 11,000 ft ; 

 ducks at 7,500, lapwings at 6,500, golden plover 

 at 6,000, and geese at 700. Although it does 

 not strictly fall within this section, the question 

 as to how far sight assists in finding a true course, 

 may be touched upon here. 



It has been stated on an authority that we 

 have unfortunately not been able to verify that 

 birds have an acuity of vision 100 times greater 

 than that of human beings. This, by the way, 

 would account for the marvellous power birds 

 like the swift exhibit of distinguishing tiny in- 

 sects on the water himdreds of feet beneath them. 



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