OF EASTERN PENNSYLVANIA. 195 



less social in its character. It is less abundant 

 than Hirundo korreorum^ and makes its appear- 

 ance about the middle of April, a little before the 

 latter. 



Its nests are placed in excavations in the banks 

 along streams, in cliffs by the sea shore, and in other 

 suitable localities. In Philadelphia they are chiefly 

 found in railroad cuttings, in clusters of a half- 



o 



dozen or more. Though more retired than many 

 of its family-relatives, this s' ( ies cannot be said 

 to be unusually shv and timid. It still retains 



s * 



much of its primitive manner:-. 



In. the sites which *\ chosen for nidihcation, 

 no little forecast is manifested. The insects which 

 are so abundant in such places, vield it an. ample 

 supply of food with but light entailment of physi- 

 cal fatigue. The stagnant water-pools which are 



O O 



r-n common along railroads, outside: th" sleepers, 

 are exceedingly prolific sources of insect-life. 



While excavating a place for a nest, the birds 

 work by turns; neither bird intermitting the 

 labor until the task is accomplished. The length 

 of time requisite to complete a cavity, depends 

 much upon the character of the earth to be re- 

 moved. It seldom exceeds four days, even under 

 the most unfavorable circumstances. The re- 

 quisite depth being attained, a circular apartment 

 is constructed and lined with feathers. 



Oviposition immediately succeeds, and is closely 

 followed by incubation which continues for 1 1 

 days. In the labor of sitting we are inclined to 



