THE SWAiLOW TEIBE. 337 



nestlings to perish. Dr. Jenner observed a pair 

 of martins which thus forsook their unfledged 

 young, and returning in the following May to 

 their old nest, had first to remove from their 

 dwelling the skeletons of the hapless little birds. 

 Strong indeed must be the mysterious impulse of 

 migration, when it can overcome the powerful and 

 better understood principle of the love of its young. 

 Who that has long watched birds can doubt of 

 their mutual comprehension of that singular lan- 

 guage which seems to our ears but a confusion 

 of sounds? Any one who pays attention to the 

 habits of young nestling birds, can perceive that 

 the parent well understands the clamorous appeal 

 of its little ones ; and among some birds, as the 

 swallow, the mother bird while in the nest seems 

 continually chirping, as if holding a conversation 

 with her family, the young evidently being as 

 familiar with the notes of their parents, as the 

 latter know the voice of their children. The birds 

 which at early dawn twitter perpetually, or as- 

 semble in the trees and twitter and chirp all day 

 long among the boughs, have a meaning in these 

 utterances, which though not definitely understood 

 by us, yet convey even to our ears tones either of 

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