Meeting Abstract
Studies of vocal behavior in temperate passerines are typically biased toward males, which are generally more vocal and aggressive than female conspecifics. ‘Duetting species,’ in which females are more vocal and active in territory defense, use highly cooperative displays that make each individual’s participation in aggressive interactions difficult to compare. Although not technically a duetting species, in Florida scrub-jays (Aphelocoma coerulescens; FSJs), males and females participate jointly, but independently, in territorial disputes using largely sex-specific calls (i.e., while both sexes use ‘weep’ calls, up to 90% of female calls are the sex-specific ‘rattle’ call), suggesting different roles in defense. Previous work with a single-speaker playback protocol showed that males and females defend equally against intruders, regardless of their sex (Ferguson, unpubl. data); however, similar to the cooperative vocalizations of duetting species, FSJs rarely engage rivals alone. We used a dual-speaker playback design to better test the roles of males and females in territorial encounters, with each speaker simultaneously playing the call of either an unfamiliar male or female FSJ to simulate an intrusion by an unknown pair. In general, males and females were equally aggressive and neither showed any bias toward male or female playback. Females, however, showed a nonsignificant tendency to call earlier in the encounter (p = 0.095) and called more (p = 0.019) than males. Some 70% of calls given by females were the rattle call. Our results further support the existence of a shared defense strategy in FSJs, but suggest an additional role for female vocalizations. Use of sex-specific vocalizations may serve to alert opposing pairs to multiple participants or as a signal to family group members in this cooperatively breeding species to recruit additional defenders.
