CHAPTER II 

 Nocturnal and Diurnal Migration 



MIGRATORY flight among birds is performed 

 by day or by night, or occasionally during 

 either, according to the species concerned. As a 

 general rule, the smaller birds migrate by night and 

 the larger ones by day, or by day or night indiffer- 

 ently. Geese and ducks often fly in migrating flocks 

 by day, but also pass in numbers after dark, especi- 

 ally during great rushes of migration when their 

 movement is at its height. The calls of geese are a 

 common sound from the darkened skies above cities, 

 heard most often in autumn, when a sudden change 

 in weather is hastening their departure for the south. 

 In the city of Washington it is not unusual in March 

 to hear the barking calls of swans at night as these 

 great birds pass in their northward travels. Among 

 my vivid memories of residence and observation on 

 the broad marshes at the northern end of Great Salt 

 Lake in Utah are the flights of ducks that passed 

 overhead in the moonlight, or the multitudes, her- 

 alded by whistling wings, that came hurtling down 

 before dawn when severe weather in the north 

 started the flight from regions in Canada. 



