THE HEIGHT AND SPEED OF FLIGHT 55 



A warbler flying leisurely, say at 10 miles per 

 hour, in a current of air which was travelling at 

 20 or more miles an hour, could accomplish the 

 journey across the North Sea say 300 miles, in ten 

 hours. Allowing much higher rates of speed for 

 strong-winged species, and greater force of wind, 

 some of the marvellous distances covered by 

 migrating birds cease to be mysterious. Prof. J. 

 Stebbins and Mr E. A. Fath made careful calcula- 

 tions from observations with the telescope, and found 

 that birds passed at rates varying from 80 to 130 

 miles per hour, and these were the minimums, 

 for if the birds were not flying absolutely at right 

 angles with the line of observation, they must have 

 travelled a greater distance in the time occupied 

 between their passage of the observation points (47). 



