FEMALE DUNNOCKS USE VOCALIZATIONS TO COMPETE FOR MALES

In songbirds, males are usually the more competitive sex and they use vocalizations to attract females and to compete with rival males. When levels of female-female competition were experimentally increased in a population of dunnocks, Prunella modularis, females were predicted t o increase their vocalization rates and to use vocalizations in compar able ways to competing males. Females produced tseep calls in territor ial conflicts with rival females, and trill calls during the pre-breed ing and fertile periods when they were left alone by their mate. Males were more likely to approach trills than tseeps, and females were mor e likely to trill than tseep in response to the song of their mate. Re moval experiments to increase polygyny showed that females produced bo th types of call more when they were competing for male attention. Thr ee out of 13 polygynous, fertile females also produced complex songs w hen their mate left to join another female. Songs were produced in the same context as the songs of female alpine accentors, P. collaris, a congener which breeds in large, polygynandrous groups where female com petition for mates is intense, and females attract males with song. Th e possible functions of the mate-attracting trills and songs of female s are discussed; in dunnocks they may (1) attract mates away from othe r females to reduce the likelihood of polygyny, (2) ensure that the ma le copulates sufficiently to cross a helping threshold, and (3) enable the female to assess future levels of parental care from her mate. (C )1997 The Association for thr Study of Animal Behaviour.