Wetland features that influence occupancy by the endangered Hawaiian Duck

Habitat loss, introduced predators, and hybridization with feral Mallards (Anas platyrhynchos) continue to threaten the existence of the endangered Hawaiian Duck or Koloa maoli (A. wyvilliana). Protection and management of core breeding areas is a recovery objective, but lack of quantitative information on the species' habitat needs hinders recovery efforts. We conducted bi-monthly surveys of 48 wetlands on private lands on the Island of Hawai'i from March 2002 to June 2003. We compared Koloa use between seasons, wetland types, and study regions and modeled how use varied with 14 site and landscape variables. Koloa occupied 54% of the surveyed wetlands; use was higher on wetlands enhanced or created for Koloa primarily through the USDA's Wetlands Reserve Program (WRP) than on ponds created for agriculture (81 vs. 41%) and on wetlands in the Kohala than in the Mauna Kea region (93 vs. 38%). Koloa were more likely to use wetlands farther (> 600 m) from houses, larger (> 0.23 ha) wetlands, and those surrounded by more wetlands area (> 1 ha). Our results (1) indicate WRP wetlands provide suitable habitat and (2) support wetlands enhancement or creation far from human disturbance. Habitat improvements combined with feral Mallard control may reduce extinction threats to Koloa.