70 BlCKXEI.L on I he Singing of Birds. [ Jaiiiiiirv 



Occasionally singularly aberrant songs are heard from the com- 

 mon Robin, in which the mellow rolling quality is entirely lost. 

 The notes are abrupt and separated, often with distinct rests, and 

 sometimes terminate with a vibratory sound suggestive of the 

 vibrant quality characteristic of the songs of our Wood Thrushes. 

 I have not been able to ascertain if these sounds regularly pro- 

 ceeded from immature throats, but if this be the fact it probablv 

 affords an instance of an ancestral character of voice retained by 

 the immature progeny of descendants. 



Individual vocal variatiun. — Undoubtedly it can be said 

 that in song, as in plumage, no two birds are precisely alike. 

 But the extreme difficulty, or often impossibility, of comparing 

 the songs of birds except through an untrustworthy mental agent, 

 is a serious obstacle in the study of this branch of the subject. 

 Nevertheless the statement that the songs of birds of the same spe- 

 cies are subject to extreme variation, and that probably no two songs 

 of different individuals of a species are identical, can be accepted 

 with little or no violence to the truth. With the members of 

 some species phonetic variation is especially evident. At the 

 season when the Song Sparrow is in full voice, I can never walk 

 with attention directed to the songs of these birds along 

 the way without being forcibly struck with the marked 

 variation shown in movement, tone, accent and other quali- 

 ties either separately or in conjunction. The same thing is 

 conspicuously true of many birds, as the Robin, the Field Spar- 

 row, the Rose-breasted Grosbeak, and others which occur in 

 sufficient numbers to afford ample scope for observation. But 

 even the same individual will show considerable variation in its 

 song at different times ; indeed not a few of our birds possess two 

 or more distinct songs. 



We are slow to give birds credit for the capacit\ of vocal ex- 

 pression which many of them possess. Writing now in the 

 autumn, with no opportunity for refreshing my memory, I can 

 recall over half a dozen distinct utterances of the common Robin, 

 and as many of the Song Sparrow. It is probable that they 

 have many more, and that birds possess a greater power of 

 oral communication than we ever suspect. 



Abnormal vocal variation. — This kind of variation, proba- 

 bly caused by imperfections of development or injuries either of 

 the vocal apparatus or adjacent structures, is perhaps not always 



