The Building of the Nest 93 



and he has been known to remedy it by attach- 

 ing a cord to the sustaining twigs and tying 

 them to a higher limb of the tree, thus 

 securing the necessary stability. 



A more familiar evidence of the intelligence 

 of birds is when the vireos are disturbed by 

 the presence of a cow-bird's egg in their 

 nest. To get rid of it, they often build a 

 new floor to the nest, and so leave the offend- 

 ing egg to spoil. But there is displayed here 

 an error of judgment that I am surprised to 

 find. The birds that take this trouble cer- 

 tainly could throw the egg out, and, I should 

 think, preserve their own eggs, which in- 

 variably are left to decay when a new struft- 

 ure is reared above the old. I believe even 

 three-storied vireos' nests have been found. 



There is one common swallow that is 

 found well-nigh everywhere, which burrows 

 into the sand ; and when we think of it, it 

 seems strange that so aerial a bird should 

 build so gloomy an abode for the nesting 

 season. This bank swallow, as it is called, 

 selects a suitable bluff, facing water, and, 

 with closed beak, turns round and round 

 with its head to the ground, thus boring 

 a hole big enough to crawl into. It turns 



