title: Calling Where It Counts: Subordinate Pied Babblers Target the Audience of Their Vocal Advertisements.
abstract: 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. Individuals 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 opportunities in non-natal groups. In the cooperatively breeding Southern pied babbler, Turdoides bicolor, most individuals who achieve reproductive success do so through taking up dominant 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 individuals 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 subordinate pied babblers adopt an alternative strategy for mate attraction by vocal advertisement from within their natal territories. We show that subordinates focus their calling efforts on the edges of their territory, and specifically near boundaries with neighbouring groups that have potential breeding partners (unrelated individuals of the opposite sex). In contrast to prospecting, calling individuals showed no body mass loss associated with this behaviour, suggesting that calling from within the group may provide a 'cheap' advertisement strategy. Additionally, we show that subordinates use information regarding the composition of neighbouring groups to target the greatest number of potential mating partners.
authors.affiliation: Department of Biological Sciences, Macquarie University, Sydney, NSW, Australia; Pied Babbler Research Project, Kuruman River Reserve, Van Zylsrus, South Africa.
authors.forename: David J
authors.initials: DJ
authors.lastname: Humphries
authors.affiliation: Pied Babbler Research Project, Kuruman River Reserve, Van Zylsrus, South Africa.
authors.forename: Fiona M
authors.initials: FM
authors.lastname: Finch
authors.affiliation: Institute of Evolutionary Biology, School of Biological Sciences, University of Edinburgh, Edinburgh, EH9 3JT, United Kingdom; Pied Babbler Research Project, Kuruman River Reserve, Van Zylsrus, South Africa.
authors.forename: Matthew B V
authors.initials: MB
authors.lastname: Bell
authors.affiliation: Department of Biological Sciences, Macquarie University, Sydney, NSW, Australia; DST/NRF Centre of Excellence at the Percy FitzPatrick Institute, University of Cape Town, Cape Town, Western Cape, South Africa; Pied Babbler Research Project, Kuruman River Reserve, Van Zylsrus, South Africa; Centre for Evolutionary Biology, School of Animal Biology, University of Western Australia, Perth, WA, Australia.
authors.forename: Amanda R
authors.initials: AR
authors.lastname: Ridley
mesh_terms: D000818:Animals; D001835:Body Weight; D001947:Breeding; D005260:Female; D008297:Male; D009068:Movement; D046109:Passeriformes / Q000254:growth & development / Q000502:physiology*; D012098:Reproduction; D014828:Vocalization, Animal