Hawaiian lobeliads (Campanulaceae; 6 genera, 126 spp.) comprise the largest plant clade of any single oceanic island or archipelago in the world, yet approximately one-fifth have become extinct. Land managers on the Island of O’ahu have been working to establish self-sustaining populations of rare lobeliads for years, however recruitment among restoration sites varies drastically. Mechanisms behind this variation may be associated with limited seed dispersal. Roughly fifty percent of Hawaii’s endemic flora rely solely on birds for seed dispersal services, yet on O’ahu all native frugivorous birds are functionally extinct. Introduced avian frugivores may serve to fill this missing role, but their relative impact on rare native plants, and how that can inform management, has not been fully studied. We investigated the diversity and abundance of birds and fleshy-fruited plants within restoration sites in comparison to the surrounding matrix, frugivory rates of endangered lobeliad fruit, and the effectiveness of luring birds to consume target fruit via playback experiments. We conducted avian, fruit, and vegetation surveys, and deployed camera and rat traps throughout restoration sites across the Wai’anae range, O’ahu, HI. Additionally, we recorded and broadcasted vocalizations of resident frugivorous birds comparing foraging behavior of control and treatment periods.
Our initial results suggest that exotic frugivorous birds dominate mountainous, forest bird communities, but rarely exploit lobeliad fruit as a resource. Local neighborhood fruiting effects may be a factor as invasive plant species are ubiquitous. We conducted 59 audio attraction experiments across 21 plant species (15 native, 6 nonnative) testing tracks of the four most abundant and widespread exotic avian frugivore. The average number of foraging frugivorous birds within 10m of a given fruiting plant was 2.64 ± 0.5 before treatment and increased to 8.46 ± 1.03 after. Birds consumed focal fruit in five percent (3 out of 59) of the audio experiments during control periods, which grew to almost 30 percent (17 out of 59) during treatment periods. The Japanese white-eye (Zosterops japonicus) was the most responsive frugivore to audio lures comprising 335 of the 517 frugivorous birds attracted, and consumed focal fruit in 14 of the 17 successful playback experiments. As such, preliminary evidence suggests that conspecific attraction may be a practical tool for land managers to foster seed dispersal mutualisms between bird and plant taxa, which could have far reaching impacts on seedling recruitment of threatened or endangered species. Data collection will be conducted until August 2017.