Geographical Variation in the Song of the Ruby-Crowned Kinglet

Abstract

VARIATION in bird song may be individual, local, seasonal, or geographical. Individual variation is by far the commonest form, and is well illustrated in the Song Sparrow (Melospiza melodia), a bird whose song seems to hold the same general characteristics everywhere throughout its range, and yet is so variable that no two individuals ever sing exactly alike. Local variation may be found in many species. I have heard greater differences in the songs of Field Sparrows (Spizella pusilla) in two Connecticut localities, not more than twenty miles apart, than there is between the average Connecticut bird, and those of Pennsylvania or Alabama. Seasonal variation is well illustrated in the Blue-winged Warbler (Vermivora pinus), the differences between the early and' late songs of this species being well known. True geographical variation, however, seems to be much rarer than the other forms. Pycraft states that such variation often been denied, but nevertheless . . . would seem to be true. 1 In my own experience there has come but a single certain case, that of the Ruby-crowned Kinglet (Regulus calendula). I have already published some facts concerning this variation (Auk, XXVIII, p. 48, and Condor, XIV, p. 31), but wider studies since then have led me to believe the fact worthy of description in a more extended article. In general, there is a distinct, certain, and constant difference between the songs of the Kinglets migrating through eastern United States, and undoubtedly breeding in eastern Canada, and those breeding in the northern Rocky Mountains. The complete geographical limits of each form of song I am unable at present to work out. I have observed the eastern song in Vermont, Massachusetts, Connecticut, New York, New Jersey, Pennsylvania, and Alabama, and on the part of a few