UCB Moorea Class: Biology and Geomorphology of Tropical Islands

Islands of the south pacific are fragile ecosystems, home to native land and sea birds that evolved in the absence of predators. On Mo’orea, French Polynesia the first humans arrived around 600 AD bringing with them invasive vertebrate predators. This study examines one of these predators on Mo’orea by observing swamp harrier (Circus approximans) habitat preference and behavior to determine if it has changed in comparison to its source population. Also it will examine their role in seabird predation on Mo’orea through a series of animal waste sample collections at high elevations. Since swamp harrier introduction in 1885 their habitat preference has not much changed from their Australian source population. The majority of its time and foraging is spent over low vegetation, though some expansion into other habitats has occurred since there are no other raptors on the island with which to compete. Feral cats (Felis catus) are also prevalent on the island and along with the swamp harriers are preying upon the native seabird populations on Mo’orea. Tahiti petrels (Pesudobulweria rostrata) and Audubon's shearwaters (Puffinus lherminieri) are being preferentially eaten by these predators over the invasive songbirds at high elevation. Feral cats appear to be the more significant predator of seabirds and without their control nesting seabird colonies may cease to exist on Mo’orea.