68 BlCKNELL on the Singing of Birds. [January 



when we may suppose the emotions of the nuptial season 

 to have waned, may we commonly witness the song-flights 

 of this species and hear the accompanying volubility of utterance 

 so diflerent from the usual song. 



In many cases some particular bodily motion or set of motions 

 accompanies the effort of song. It may not be irrelevant here to 

 query whether this combined vocal and bodily activity, so often 

 observable., is to be regarded as resulting from an intensity of 

 emotion which fails to find satisfactory relief through a single 

 source of expression, or whether song be ever from physiological 

 necessity dependent on muscular action additional to the activity 

 of the vocal organs. We often observe during a song-flight a 

 tendency to greater bodily action than is required for simple 

 flight. Indeed, I have seen such motions so marked in the case 

 of the Orchard Oriole as strongly to suggest the Chat. The same 

 may be said of the Maryland Yellow-throat. But undoubtedly 

 the effort of singing on the wing, by disturbing the natural motion 

 of flight and retarding tlie progress of the bii-d through the air, 

 has much to do with the unusual demeanor of most species during 

 the song-flight. The song-flight certainly argues some forcible 

 mental process in the actor. That birds are subject to sudden 

 and intense subjective motions, we cannot doubt. 



Articulate or vocal variation in birds may be of five principal 

 kinds. These may be designated as geographical, seasonal, 

 individual, variation with age, and abnormal. As the present 

 paper is intended to treat primarily of the times and seasons of 

 song, each of these kinds of variation will be only briefl}^ touched 

 upon here as connected with and partially introductory to the 

 general subject. 



Of Geographical variation little can be said. Up to the 

 present time it has hardly been formally recognized as in any 

 way general, and though well illusti-ated in the case of certain 

 birds, our knowledge of it is slight. It is, however, probably 

 more general than has been supposed, and it is not by any means 

 improbable that ultimately it may be found susceptible of formula- 

 tion in special laws, as physical variation has been. 



Perhaps the best exponents of vocal variation with longitude 

 are our forms of Sturnella. While there appears to be no such 

 conspicuous instance of vocal variation with latitude, such varia- 

 tion has been observed and recorded in the case of a few spe- 

 cies. 



