Female dunnocks use vocalizations to compete for males

In songbirds, males are usually the more competitive sex and they use vocalizations to attractfemales and to compete with rival males. When levels of female-female competition were experimentallyincreased in a population of dunnocks, Prunella modularis, females were predicted to increase theirvocalization rates and to use vocalizations in comparable ways to competing males. Females producedtseep calls in territorial conflicts with rival females, and trill calls during the pre-breeding and fertileperiods when they were left alone by their mate. Males were more likely to approach trills than tseeps,and females were more likely to trill than tseep in response to the song of their mate. Removalexperiments to increase polygyny showed that females produced both types of call more when they werecompeting for male attention. Three out of 13 polygynous, fertile females also produced complex songswhen their mate left to join another female. Songs were produced in the same context as the songs offemale alpine accentors, P. collaris, a congener which breeds in large, polygynandrous groups wherefemale competition for mates is intense, and females attract males with song. The possible functions ofthe mate-attracting trills and songs of females are discussed; in dunnocks they may (1) attract matesaway from other females to reduce the likelihood of polygyny, (2) ensure that the male copulatessuYciently to cross a helping threshold, and (3) enable the female to assess future levels of parental carefrom her mate.

N. E. Langmore & N. B. Davies, Anim. Behav., 1997, 53, 881-890