WEST 



length of each migratory flight. The average daily intake of small 

 birds probably remains relatively constant throughout the year, 

 since energy demanding activities such as existence in winter cold, 

 deposition of fat, migration, reproduction, and molting are uni- 

 formly spaced. The distribution of a species is therefore limited 

 to locations where the climate permits fulfillment of all essential 

 energy demanding activities. 



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