Habitat Characteristics of Refuge Wetlands and Taro Lo\u27I Used By Endangered Waterbirds At Hanalei National Wildlife Refuge, Hawai\u27i

Hanalei National Wildlife Refuge (HNWR) was established to protect habitat for the endangered Hawaiian common moorhen (Gallinula chloropus sandvicensis), Hawaiian coot (Fulica alai), Hawaiian duck or Koloa (Anas wyvilliana), and Hawaiian stilt (Himantopus mexicanus knudseni). I studied two major habitat types (refuge wetlands and taro lo’i) used by these endangered waterbirds (EWBs) as well as wetland vegetation and EWB response to moist-soil management at HNWR. Furthermore, the links are discussed between habitat conditions that occur during the taro agricultural cycle and how each stage contributed to the life-history requirements for foraging, loafing, and nesting of these four EWBs. During the study, effective management of refuge wetlands at HNWR was not possible because the water control infrastructure did not allow for the effective transfer or discharge of water needed to promote optimal habitat conditions for all EWBs. As a result, invasive plant species dominated most of the wetland management units. A few wetland subunits (3.3 ha) did have rototiller treatments combined with water level manipulations in an attempt to create conditions for the germination of native and/or naturalized vegetation. These manipulations produced moist-soil vegetation such as the annual sedge, fimbry (Fimbristylis littoralis), or the perennial knotgrass (Paspalum distichum). Moorhen were commonly observed foraging in F. littoralis or P. distichum. Koloa also were observed feeding and loafing in F. littoralis after water levels were raised to overtop seedheads. The majority of EWBs were observed foraging or loafing on grass-covered dikes surrounding taro because frequent mowing encouraged vigorous plant growth and increased visibility of predators. Moorhen preferred lo’i being harvested and stilt preferred unvegetated wet fallow lo’i; whereas, coots and Koloa preferred vegetated wet fallow lo’i. EWBs may prefer open water conditions in these taro habitat categories because they provide important invertebrate food resources for breeding and brood-rearing. Moorhen preferred less intensively managed taro lo’i in early growth or mature and medium to dense growth stages because these habitats provided structural support for overwater nests and the complex habitat structure for invertebrates. Furthermore, annual wetland plants also provide forage for moorhen, coot and Koloa. Call response surveys indicated that moorhen were more abundant in taro lo’i (3.6 birds/ha) compared to refuge wetlands (1.6 birds/ha); however, wetland infrastructure was not in place throughout the study to promote optimal conditions in all refuge wetlands. Taro lo’i in early growth or mature and medium to dense growth stages provided important cover and obscurity for 41% (24 of 58) of the moorhen nests found throughout the study. Nest success for moorhens was 64%; however, recruitment may have been as low as 2.5%, likely as result of predation