Sex-differences in timing of the black-capped chickadee fee-bee song

Abstract

Male black-capped chickadees produce fee-bee songs in spring for mate attraction and territorial defense. Less is known about the female song use in this species although a version of song, soft-song, appears to be used in mate-mate communication. Recent analyses of songs produced by chickadees revealed that female fee-bee songs are distinct from male songs in the spectral domain. Chickadees also precisely control the timing of their fee-bee songs during territory defense. No previous work has explored whether there are sex differences in the temporal patterning of fee-bee song production. Inter-song intervals were extracted from recordings of fee-bee songs produced in non-social contexts by 8 male and 7 female birds. Male chickadees produced fee-bee songs regularly, with the majority of songs spaced at intervals of 2.5–5.0 s. Song timing by females was more variable with production intervals ranging from 1.5 to 8.0 s. The relative stereotypy of song timing by males is consistent with earlier work suggesting that males may modulate song timing to communicate with other birds (e.g., by timing song production to either reduce or increase the likelihood that their songs overlap with those of other singers), and with differential use of songs by males and females.