Anderson, S. H.; Kelly, D.; Robertson, A. W.; Ladley, J. J.; Innes, J. G. In press. Birds as pollinators and dispersers: A case study from New Zealand. Acta XXIII Congressus Internationalis Ornithologici .
Abstract
New Zealand’s long biogeographic isolation has left a legacy of distinctive flora and fauna. The flora is characterised by a high percentage of trees (33% of species), a high percentage of bird-dispersed species (72% of trees), and a low incidence of ornithophily (4% of genera). In the pre-human avifauna, twelve species dispersed seed, and five species were pollinators. Native ecosystems have since suffered from clearance of 71% of forests, extensive hunting, and the widespread occurrence of 14 introduced predatory or browsing mammals. As a result pollinating and seed dispersing birds are either regionally or nationally rare (7 species) or extinct on the New Zealand mainland (6 species). Six of seven bird-pollinated plant species examined so far are pollen-limited to some extent at mainland sites. Three of eight fruiting species studied are suffering reduced dispersal on the mainland, and large (>1.4 cm) diameter fruits now depend on a single disperser (NZ pigeon, Hemiphaga novaeseelandiae). Conservation of these plants requires management of native bird populations (especially tui Prosthemadera novaeseelandiae, bellbirds Anthornis melanura, and NZ pigeon) to avoid long-term shifts in vegetation composition. Intensive predator control has been shown to increase the densities of mutualist bird species, suggesting that New Zealand conservation managers can augment bird-serviced plant populations by predator control, a third-order ecological manipulation.
Keywords
bird pollination, bird dispersal, mutualisms, New Zealand