THE TRAVELS OF BIRDS 



would be overflowing with young Swallows, 

 which, in this snug retreat, seemed to be removed 

 from the many dangers which beset nestling 

 birds. 



So each season, beside the forty-odd old birds, 

 some eighty young ones probably left this hovel 

 to join others of their kind on the great journey 

 to the tropics. But the following spring only 

 forty-odd birds returned to the loft. What be- 

 came of the others? 



There were no colonies of Barn Swallows near 

 by; nor, so far as I know, were any new ones 

 started. Furthermore, in spite of their safe, 

 well-protected nesting places, Barn Swallows 

 did not seem to increase in the neighborhood. 



So I could tell you of other bird communities 

 with which I am familiar. Year after year many 

 more birds leave in the fall than return in the 

 spring; and we may well ask why so few come 

 back. 



Birds, of course, like other animals, are mor- 

 tal, and each year a certain proportion of them 

 die, but we must find other causes than death 

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