NOCTURNAL MIGRATION 6i 



to 42 seconds, or at the rate of 17 1.4 to 200 miles per 

 hour. These jfigures may offer some solace to those 

 who, like myself, have expended considerable am- 

 munition in collecting specimens of the white- 

 throated and other swifts as they circled in the wind 

 over high ridges or mountain headlands. 



Most birds when frightened are capable of in- 

 creasing their speed above the figures indicated, to 

 enable them to escape momentary perils, • — per- 

 haps for short distances to double the normal rates, 

 — but cannot long maintain such exaggerated 

 efforts. It is certain that migrations are performed 

 at the usual rate of normal flight, as by pursuing 

 this steady course birds conserve their strength and 

 avoid the fatigue and exhaustion that undue speed 

 would entail. Eagle Clarke has recorded that mi- 

 grants passing lightships flew without hurry or 

 strain to attain speed, though their flight was at- 

 tended by businesslike method, without delay. 



If we consider ten hours as a fair stretch of flight 

 over land, the speeds cited would carry crows 310 to 

 450 miles in a ten-hour day, the smaller birds from 

 200 to 370 miles, ducks from 440 to 590 miles, and 

 geese from 420 to 550 miles — considerable dis- 

 tances when direct airlines are considered, that 

 would cover the ordinary migration route from 

 Canada or the northern states south to the Gulf 

 Coast, Central America, the West Indies, or even 



