264 LIFE-HISTORIES OF BIRDS 



which he reared from the nest, that was trained to 

 vary and modulate its song in time with the move- 

 ments of the index finger, increasing and decreasing 

 the volume of song by the elevation and depression 

 of the finger, and accelerating and retarding the 

 time by the lateral movements of the same. 



In Eastern Pennsylvania, according to our ex- 

 perience, but a single brood is raised in a 

 season. The time of nidification is somewhat ir- 

 regular, commencing sometimes as early as the 

 1 5th of May, but generally from the loth to the 

 1 5th of June. Nests have been taken with eggs 

 as late as the i2th of July, and occasionally with 

 young during the last week of August. These 

 delays were doubtless, due to the fact that the 

 authors of such nests had been frustrated in their 

 early endeavors. The destruction of a nest whilst 

 incubation is progressing, will generally lead to 

 the renewal of the attempt in some other place; 

 the desire for offspring triumphing over the 

 most insuperable difficulties. We have known 

 instances where the same pair had been baffled 

 four times in succession, and as often renewed 

 the attempt. Again, where adverse circumstances 

 have operated against the fulfilment of this 

 important business, the birds have been com- 

 pelled to abandon their labors unwillingly, before 

 the consummation of the task. 



Perhaps an unfortunate female or male has 

 been doomed to lead the life of a celibate, by reason 

 of the scarctiy of individuals of the opposite sex. 



