Why Birds Come and Go 

 HOW IS THEIR CALENDAR REGULATED? 



In spite of this constant shifting of the feathered 

 population, there is astonishing system and punctu- 



"A cold exposure" Redpoll on a cedar tree 



ality of appearance and disappearance of the greater 

 part of it, one discovers on keeping a bird diary, 

 which, by the way, is even more interesting than 

 Pepys's. For thirty years the purple martins reached 

 a certain home set up for their benefit in a New 

 Jersey garden, on the 26th, 27th, or 28th of April, 



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