NOCTURNAL MIGRATION 57 



there Is great mortality. Such storms are more 

 dangerous in their effect on food-supply than in the 

 cold that they bring, as most species of birds can 

 endure cold if they are properly fed. 



With some species the return southward in au- 

 tumn comes long before there is any cold. Yellow 

 warblers, Baltimore orioles, kingbirds, the Euro- 

 pean cuckoo, and many shore-birds, in both eastern 

 and western hemispheres, crowd south before the 

 close of summer, when there is no meteorological 

 change to warrant it. Others linger until cold nights 

 and frosts warn of approaching extremes, and then 

 move south rapidly. Some linger until cold storms 

 actually strike their northern ranges. 



Movement among these later migrants is noticed 

 especially in areas immediately south of the belt 

 where cold winters are prevalent. In southeastern 

 Kansas, at the northern edge of the Austro-riparian 

 life-zone, during November and December new 

 arrivals among migrant sparrows, thrushes, and 

 blackbirds are noted with every storm reported in 

 the north, indicating that many birds linger in the 

 north to the last possible moment. Similarly, freez- 

 ing weather far north is frequently responsible for 

 great flights of ducks or of Wilson's snipe to southern 

 areas, where the birds arrive in abundance before 

 the press of severe conditions in regions to the 

 northward. 



