ORIGIN OF SONG 157 



number of different physiological contrivances ; 

 for if the difference were really attributable to 

 some structural peculiarity, then the range of 

 sounds embraced in the call-notes and the sexual 

 call of any given species, must be the measure 

 of the capacity of its instrument ; and no matter 

 how great its power of imitation may be, it 

 follows that it will only be capable of copying 

 those sounds which fall within that range. 

 There is plenty of evidence to show that the 

 power of imitation is almost unlimited, at all 

 events that it is not confined within such 

 narrow limits as are here demanded. Hence 

 it seems clear that the diversity of song is 

 not to be sought in structure, but in some 

 innate capacity to play one tune in prefer- 

 ence to another ; and if this be so, and if 

 out of the same instrument, which has been 

 primarily evolved to further the biological end 

 of intercommunication, all manner of diverse 

 sounds can be made to proceed, the problem 

 of the oi'igin of song is to that extent 

 simplified. 



We must next inquire into the nature of 

 song, and endeavour to ascertain whether all 

 the individuals of a species are alike proficient, 

 or, failing this, whether there is any quality 

 which can be observed to be constant under 

 all conditions. I watch the Reed-Buntings in 

 a marsh and find that there are three males 

 occupying adjoining territories. Two of them 

 are fully mature and their plumage is bright : 

 that is to say the crown is black, the collar 



