174 THE WONDER OF LIFE 



3,000 feet. Some astronomers, however, report seeing 

 birds at elevations of 10,000 feet. 



Gatke estimated the speed of migrating plovers, curlews, 

 and godwits, crossing Heligoland, at nearly four miles a 

 minute, and he calculated the speed of Hooded Crows, 

 crossing the North Sea, at 108 geographical miles per hour. 

 He credited the little Northern Bluethroat with a 

 velocity of 180 geographical miles per hour. It seems 

 to be the general opinion of experts that these figures 

 are far too high. Dr. J. Thienemann's observations at 

 Rossitten in 1909 led to such averages as the following : 

 Sparrow-Hawk, 25 miles per hour; Hooded Crow, 31 J; 

 Rook, 32| ; Chaffinch, 32|; Linnet, 34f; Peregrine Falcon, 

 37; Jackdaw, 38J ; Starling, 46. Some other careful 

 observers have estimated the migratory rate of many birds 

 at about a hundred miles an hour. It is reported that a 

 marked swallow flew from Compiegne to Antwerp, about 

 145 miles, in 1 hour 8 minutes ! 



It is certain that many a bird may attain in its everyday 

 life to a velocity of fifty miles an hour, and it is probable 

 that twice as fast is a safe estimate for the rate of many a 

 migratory flight, when the whole life is raised to a higher 

 pitch. 



And as to meteorological conditions it becomes increas- 

 ingly clear that birds in their migrations are somewhat 

 strikingly indifferent to the weather, unless,indeed, it reaches 

 a high degree of storminess or f ogginess or unpropitiousness 

 generally. It seems that the weather- conditions which 

 obtain when and where a mass-movement begins are of 

 much more moment than those into which the birds pass 

 in the course of their flight. 



Deeper Problems of Migration. It is interesting to 



