RESEARCH ARTICLE Calling Where It Counts: Subordinate Pied Babblers Target the Audience of Their Vocal Advertisements

For territorial group-living species, opportunities to reproduce on the natal territory can be limited by a number of factors including the availability of resources within a territory, access to unrelated individuals, and monopolies on reproduction by dominant group members. Indi-viduals looking to reproduce are therefore faced with the options of either waiting for a breeding opportunity to arise in the natal territory, or searching for reproductive opportuni-ties in non-natal groups. In the cooperatively breeding Southern pied babbler, Turdoides bicolor, most individuals who achieve reproductive success do so through taking up domi-nant breeding positions within non-natal groups. For subordinate pied babblers therefore, searching for breeding opportunities in non-natal groups is of primary importance as this represents the major route to reproductive success. However, prospecting (where individu-als leave the group to search for reproductive opportunities within other groups) is costly and individuals rapidly lose weight when not part of a group. Here we demonstrate that sub-ordinate pied babblers adopt an alternative strategy for mate attraction by vocal advertise-ment from within their natal territories. We show that subordinates focus their calling effort