Does 'acoustic anchoring' reduce post-translocation dispersal of North Island robins?

Abstract

Context Animal translocations are an important conservation tool; however, post-release dispersal can hinder successful population establishment. Playback of conspecific song attracts dispersing individuals in some species, although its application following animal translocation has yet to be rigorously investigated. Aims To determine whether conspecific song can be used as an ‘acoustic anchor’, we adopted an experimental approach during the translocation of 60 North Island robins (Petroica longipes). Methods At one of two release locations, we broadcast song at natural rates from four speakers (4 h per morning), for 9 days following release; we set the second release location as a control where identical conditions were established but no playback occurred. To assess the impact of playback, we monitored speaker and control locations, surveyed tracks around the release areas, and radio-tracked robins over nine playback days and an additional 9 days. Key results Most robins left both immediate release areas; however, our results showed that (1) more robins (6 birds on 14 of the 18 days), in particular females (3 birds), approached the playback location than the ‘flagged’ control location (3 male birds on 5 of the 18 days), (2) individual robins returned to the playback location repeatedly, unlike those at the control site, and (3) robins also visited the playback location longer after playback than they did silent control locations. In contrast, radio-telemetry data from five robins suggested that general dispersal was not influenced by playback. Two radio-tracked females moved over long distances (some to >3 km from their release location), whereas two radio-tracked males remained relatively close to the release sites. Conclusions We demonstrated a short-term attraction effect of playback over a period of several weeks for some birds, particularly females. In contrast, we detected fewer birds over a shorter period at the silent control release site, where no females were detected. However, long-term monitoring at both sites suggested that the effect of playback on reducing post-release dispersal was transitory. Implications The lack of a clear and lasting effect of acoustic anchoring on dispersal in the present study has provided information on the limited utility of song playback as a conservation management tool for this species. Consideration of the species’ ecology and suitability for ‘acoustic anchoring’ must be made before playback is employed as a conservation measure to reduce excess post-translocation dispersal.

Responses of Eastern Yellow Robins Eopsaltria australis to translocation into vegetation remnants in a fragmented landscape.

“…In particular, they should quantify habitat at release sites, including the ground layer, which is important for robin foraging but not assessed by us (e.g., see Recher et al 2002;Cousin 2004a;Antos et al 2008). We also suggest that playback of robin songs may increase the likelihood of robins remaining at release sites, as used by Bradley et al (2011).…”

“…However, translocation and release into uninhabited sites have been used extensively with robins Petroica spp. in New Zealand, with high success (e.g., Armstrong and Ewen 2002;Armstrong and Davidson 2006;Bradley et al 2011).…”

Incorporating Allee effects into reintroduction strategies

“…comm. ; Bradley et al 2011), and captive-reared animals often have higher post-release mortality than wild animals (Snyder et al 1996). Ongoing research in this area will hopefully improve our predictive capabilities, but it would be rash at present to assume that any management will effectively reduce post-release dispersal or mortality unless this has been demonstrated in a similar species and system.…”

Sensory‐based conservation of seabirds: a review of management strategies and animal behaviours that facilitate success

“…Amongst songbirds, conspecific vocalizations have been effective attractants for translocation and anchoring (Ward & Schlossberg, ). A notable study on translocated New Zealand robins ( Petroica australis ), involved control sites and clearly demonstrated that more individuals returned to locations with conspecific playback (Bradley et al ., ). Marine animals have similar sensory constraints as seabirds and have also been studied from a sensory‐based conservation approach using auditory stimuli.…”