Restoring bird pollination of Fuchsia excorticata by mammalian predator control

Many restoration projects aim to increase populations of native fauna and flora, but benefits to the ecological interactions between species are unknown. The restoration of bird pollination services to Fuchsia excorticata (tree fuchsia) was examined at Maungatautari, in the Waikato Region, New Zealand. At Maungatautari, a pest-exclusion fence encloses ~3400 ha of native forest, within which most mammalian pests were eradicated between 2004 and 2007. In December 2010, 140 five-minute bird counts at Maungatautari and a non-treatment site, Pirongia Forest Park, indicated that tūī (Prosthemadera novaeseelandiae) and bellbirds (Anthornis melanura), key pollinating species, were significantly more abundant at Maungatautari than Pirongia. We then examined whether greater bird numbers at Maungatautari translate into enhanced bird services. A previous study correlated visual pollen scores on F. excorticata flowers to fruit set, allowing rapid assessment of pollination levels. Pollination service to F. excorticata was significantly greater at Maungatautari, with good pollen loads on the stigmas of both female and hermaphrodite flowers there, compared with inadequate pollination on both sexes at Pirongia. Observations of bird visitors to F. excorticata flowers found significantly higher visitation rates at Maungatautari than Pirongia, consistent with the better pollination levels. Pollination levels of F. excorticata were compared with data from 68 sites from around New Zealand with a range of mammalian predator control levels. Sites that were pest-fenced, islands, or mainland islands (and assumed to have lower densities of mammalian pests) had good pollen scores on female plants, whereas at unmanaged sites females had inadequate pollination. This study indicates that higher abundance of pollinating birds as a result of mammalian pest control restores the pollination service to F. excorticata.