18S4.] l)iCKNF.i.i. on ///!■ S/i/o/mr of Dirds. 6 '2 



Tlierc arc facts which sccnis to indicate that \ocal disahilitv 

 often accompanies the moult, thus imposin<i; silence until power 

 of voice is g-radually regained with the renewal of plumage. 



In its origin and use, song is undoubtedly to be classed as a 

 sexual character, in the same category as the adornments of the 

 plumage in the male bird. (It is not necessary here to consider 

 the singing of the female of certain species, tliis I)eing entirely 

 secondar}' to the present consideration.) Taking this view of the 

 song we can understand whv with those species, the males of 

 wdiich undergo great semi-annual mutations in the color of their 

 plumage, — in the fall assuming the plainer garb of the female, — 

 have no second song period : attired like the females, they are, like 

 them, songless. May we construe this fact as evidence that the 

 silence of many birds in the autumn is not voluntary, but that the 

 vocal function is lost with the other attributes of masculinity .'' It 

 does not necessarilv fdlow that male song birds are always songless 

 when not attired in their nuptial costume. The males of some 

 species while in immature plumage are equally melodious with 

 the adults in full dress. But vsdiile I have never been able to study 

 satisfactorily many cases bearing clearly on this point, I have ob- 

 served in several instances that in apparently immature males 

 which sang, the plumage, though that of the young bird, ex- 

 ceeded in color that of the female of their species. In other cases 

 it seemed probable that sexual maturity had anticipated the phase 

 of most highly developed plumage. The Purple Finch sings 

 while attired in the plumage usuallv regarded as characteristic of 

 the young male, but I have heard no songs from birds in this con- 

 dition of plumage which did not show evident immaturity of ex- 

 pression. The female of this species also has been been said to 

 sing. With species the females of which sing, we should expect 

 the young male to have equal use of its voice. 



But in these considerations we must not forget that our know- 

 ledge of the real significance of color-changes of plumage is but 

 meagre, and that color-phases of plumage are not in all cases true 

 to their usual indications in regard to the age of their subjects. I 

 do not wish to be understood as stating that the males of all of 

 our birxls which in the autumn change to the plainer colors of 

 their mates invariably cease to sing. There are at present no 

 data upon which so general a statement can be based, and were 

 the necessary data at hand not improbably exceptions would be 



