A SHORT STUDY OF BIRDS' NESTS. 135 



cepting the only alternative, they availed themselves of 

 a hollow chestnut-tree, where they were, to all appear- 

 ance, as well suited as they would have been in their 

 former haunts. My curiosity was roused to know what 

 the following summer would have to show. Would they 

 return to the tree ? In April and May of 1870, I care- 

 fully watched for them, but not a swallow appeared. 



The nests of the chimney-swallows, when placed in 

 hollow trees, are, of course, greatly exposed to the attacks 

 of owls and such carnivorous mammals as are good 

 climbers, and it is highly probable that, in the case of 

 these birds, we have an instance of birds thriving better 

 and increasing in numbers, in consequence of the envi- 

 ronment being greatly altered by man's agency. The 

 habit of building nests of a particular pattern and many 

 together has remained the same ; but, the artificial locali- 

 ties offered being a great improvement over anything in 

 .Nature, the birds have been correspondingly benefited. 



