264 LIFE-HISTOKIES 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 decrefising 

 the volume of song by the elevation q.nd depression 

 of the finger, and accelerating and retardi^ig 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 nidificatipn is somewhat ir- 

 regular, commencing sometimes as esjrly as the 

 15th of May, but generally from the loth to tlje 

 15th of June. Nests have been taken witb eggs 

 as late as the 12th 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 ofte,n renewed 

 the attempt. Again, where adverse circumstances 

 have operated against the fulfilment of this 

 important business, the birds have been cow 

 pellpd to abandon their labors unwillingly, before 

 the consupimation of the task. 



Perhaps an unfortunate female or male has 

 beer) doomed to lea4 the life of a celibate, by reason 

 of the scarctiy of individuals of the opposite sex. 



