

Nights are rarely so dark that terrestrial objects 

 are totally obscured. 



of study, of course, is limited to fine weather and to periods of the moon. 

 Lowery reports that "night migrants fly singly more often than in flocks, 

 creating a remarkably uniform dispersion on a local scale, quite unlike the 

 scattered distributions observable in the daytime." All our evidence for 

 ducks, geese, and swans, however, suggests that they hold their flock forma- 

 tions after nightfall, and that mass movements of flocks remain cohesive 

 after dark. There are many species which, like the Coot, travel singly; but 

 these individual birds, nevertheless, make up aggregations of migrants that 

 apparently fly within hearing distance of one another. The Nevada catas- 

 trophe of grebes testifies to the grand formations of night migrants; and 

 once at Ithaca, New York, during an autumn dawn, I saw an armada of 

 Common Loons coming out of the north, a loose formation of birds that 



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