Birds select habitat based upon a combination of direct resource cues and indirect social cues (i.e. the presence of conspecifics). Conspecific attraction is the tendency for individuals of the same species to aggregate near one another. This behavior has been successfully exploited by conservation practitioners to augment threatened or endangered populations of colonial seabirds and migratory songbirds by establishing breeding territories. Common methods of attracting avian conspecifics using social information include decoys and/or playback of vocalizations. Recently, there has been a growing body of literature surrounding social information use and habitat selection among foraging birds. It has be discovered that lizards, monkeys, and birds are attracted to fruiting trees that broadcast vocalizations of frugivorous birds. Fruit-eating animals can influence plant recruitment by enabling germination, reducing seed mortality near parent plants due to disease or competition, facilitating colonization of new sites, and increasing gene flow between isolated populations. However, to date no study has investigated if frugivory by birds can be augmented using audio playback experiments. The potential of artificially inducing frugivory of specific fruiting plant species could have far-reaching implications for management of ecosystems with eroding seed dispersal networks or fleshy-fruited plant populations with limited dispersal.
Results/Conclusions
Our study was conducted from June 2016 – July 2017 across Oahu, Hawaii. All native frugivorous bird species are extinct on this island, but several exotic, fruit-eating species have become naturalized and were the focal bird species used for our experiments (Japanese white-eye; red-billed Leiothrix; red-vented bulbul; red-whiskered bulbul). We conducted 80 acoustic, playback experiments across 25 native and exotic plant species. The average number of birds that consumed fruit from a target plant per trial during the control period was 0.13±0.08 and increased to 1.58±0.5 during the treatment period. Almost 90% of all observed frugivory events were of ‘common’ plants suggesting that fruit familiarity may be a driver of seed dispersal. Abundances notwithstanding, more than half of the 996 frugivorous birds attracted during treatment periods consisted of Japanese white-eye and of the 129 birds observed eating fruit from focal plants, 97 were white-eyes as well implying that some birds may use social information more than other species. Roughly 30% of the experiments were successful suggesting that audio lures may be a practical tool for land managers to foster seed dispersal mutualisms between bird and plant taxa. This was a proof-of-concept study and more research is needed to determine feasibility.