44 LIFE-HISTORIES OF BIRDS 



been found by us, securely located within the 

 forked branch of an apple-tree. 



Why should the Blue Bird select a hollow or 

 perforated limb for its nest? The answer to this 

 query is not far to reach. Being an early visitor, 

 such situations secure the requisite warmth and 

 shelter for the eggs and young. They also 

 guarantee protection from rapacious birds. But 

 other species of equal size and less brave, nidificate 

 in open and exposed situations, without encounter- 

 ing more than ordinary opposition. The bright 

 azure blue of the female, which is triflingly less 

 than that of her partner, would render her a con- 

 spicuous object to the keen gaze of rapacious 

 birds. Therefore, to insure security against 

 attack, advantage has been wisely taken of 

 hollows in the trunks and branches of trees. 



The female Indigo Bird contrasts as favorably 

 with the male. Now this species constructs its 

 nest in thick brier-bushes ordinarily, and fares 

 equally well. May not such bushes secure the 

 same protection? We think they do. 



From facts which we shall shortly present, we 

 incline to the opinion that in primitive times, 

 hollow trees were more generally chosen than at 

 present, on account of the security which they 

 guaranteed against the predacious attacks of birds 

 and the inclemency of the weather. Sialia Mexi- 

 cana, the nearest relative of our eastern species, 

 according to the authorities of Drs. Cooper and 

 Kennedy, are common in our Western Territories 



