Plant-Animal Interactions on Hesperomannia oahuensis

Hesperomannia oahuensis is an endangered, bird pollinated tree or shrub endemic to the Waiʻanae Mountains of Oʻahu, Hawaiʻi. Severe drought, changing forest composition, ungulate damage, loss of pollinators, and low fitness are contributing factors to the steep decline of wild H. oahuensis populations. The wild population has declined from 96 plants to 2 since 1977. Over the past thirteen years, the Army Natural Resources Program Oʻahu (ANRPO) has created four reintroductions and outplanted 274 H. oahuensis. Annual monitoring and fruit collection have returned few filled achenes from the outplants, despite threat control targeting ungulates, rats, and weeds, suggesting that pollinator services are lacking. To obtain viable seed for ex situ storage and propagation, hand pollination has been the norm. To confirm more recent field observations of endemic forest birds interacting with H. oahuensis flowers this project was initiated to investigate the pollination ecology of reintroduced H. oahuensis and test the potential of birdsong playback to attract more pollinators. For three flowering seasons, ANRPO has installed game cameras around a H. oahuensis reintroduction site to record videos of flower visitors. We set up a speaker system to project ʻapapane and ʻamakihi birdsong at regular intervals every other day for the duration of the flowering season. Field team visited the site every other week to reposition cameras on open flowers, switch out batteries and SD cards. Since 2021, we have recorded over 45,000 videos, with 1000 videos of animals interacting with flowers. In this presentation I will report on the current status of this endangered taxon, project methodology, and present preliminary results.