SINGING AND ITS FUNCTIONS IN FEMALE WHITE-CROWNED SPARROWS

Singing by female oscines is thought to be rare in north temperate latitudes. Colour-marked female white-crowned sparrows in two subspecies populations were studied: Sedentary coastal Zonotrichia leucophrys nuttalli at San Francisco and migratory montane Z. l. oriantha at Tioga Pass, Sierra Nevada, California. Female Z. l. nuttalli sang regularly during the autumn, winter and early spring months prior to the onset of nesting activity. This extended period of singing during the non-breeding season suggests that female song is not an epiphenomenon related to hormonal changes just prior to the reproductive period. Females both produced spontaneous song and responded to playback with singing. Female songs differed from those of males in various frequency and temporal parameters. Female Z. l. nuttalli appeared to sing to defend territories against inserting birds-of-the-year, or to advertise for mates. A few females sang more than one song type and matched themes with mates during countersinging bouts. Females of Z. l. oriantha were observed singing in early summer upon arrival on their breeding grounds and during periods of late snow melt when nest sites were in short supply. Female songs in this subspecies were more male-like than those of the sedentary Z. l. nuttalli females. Due to the short breeding season, females of the migratory subspecies defend territories more intensely than do females of the sedentary form, which may account for the use of more male-like song in this subspecies. © 1993 The Association for the Study of Animal Behaviour. All rights reserved.