Research Projects
Nesting Time Impacts Nest Depredation of the Hawaiian Stilt in Wetland on O'ahuNest depredation is the leading cause of nest failure in avian species and may be impacted by where and when birds decide to breed. In many studies, nest depredation is influenced by the timing of the nesting season and by nest site features, such as proximity to water and vegetation height. The Hawaiian Stilt (Himantopus mexicanus knudseni) is an endangered Hawaiian waterbird that nests in wetlands across the Hawaiian Islands from February to September. The nesting season coincides with a seasonal decline in precipitation, which may impact depredation rates, and thus nest survival. In this study, we used observational surveys and nest cameras to examine the impact of nest-site characteristics and nest initiation date on nest depredation of the Hawaiian Stilt.
We found that stilts preferred shorter vegetation and preferred to nest in Pickleweed (Batis maritima) and Water Hyssop (Bacopa monnieri) rather than other available plant species. However, nest-site characteristics, such as vegetation height and distance to water, did not have an impact on depredation risk. Early nests had a higher chance of survival than late nests, and the number of depredated nests peaked later in the nesting season. Introduced mammals were the primary nest predators. Increasing predator control later in the Hawaiian Stilt nesting season, particularly for mammalian predators, may increase nest survival of later nesters. Our study suggests that, despite longer nesting seasons and year-round occupation of wetlands, early nesters in subtropical regions may have higher nest survival than late nesters, similar to trends observed in temperate regions. |
Water Diversions: Economic Opportunities and Ecological Trade-offsIn Hawai‘i, watersheds are an important natural resource, providing ecosystem services to residents, including irrigation for agriculture, as well as habitat for native species. On the windward side of O‘ahu, an irrigation system diverts water from Maunawili Watershed into Waimanalo for agricultural use. Kawainui Marsh, a large component of Maunwili Watershed, provides primary nesting and foraging habitat for Hawaii’s native waterfowl, including three endangered waterbirds. In this study we are evaluating trade-offs between ecosystem services provided by Kawainui Marsh and economic changes in Waimanalo agriculture due to the transfer of water. Results from this study may be used to inform watershed management decisions in Hawai‘i, and may be applied to other watersheds with similar management tradeoffs.
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The Potential for Indigenous Resource Management to Aid in Recovery of Endangered Hawaiian WaterbirdsConventional conservation practices often separate people from landscapes, assuming that minimal human interaction is optimal for recovery of endangered species. However, conservation practices that are based on social-ecological frameworks may be more successful than exclusionary conservation practices, as they are more likely to encompass working landscapes and the people in them, thus increasing social support. Indigenous agroecosystems are social-ecological systems that have received growing attention as tools for preserving biodiversity. Following the arrival of Polynesians to Hawai‘i, lowland forests and alluvial plains were converted into flooded-fields (lo‘i) for cultivation of taro and other resources, which greatly expanded wetland habitat used by waterbirds. Restoration of lo‘i through Indigenous resource management practices may aid in the recovery of endangered, native waterbirds, which are threatened by the loss of available nesting habitat from rising sea levels. In this study, we are using existing GIS layers to spatially and quantitatively map (1) the area of potential waterbird habitat in Hawai‘i likely to be lost due to sea level rise by the year 2100; and (2) the area of potential waterbird habitat in Hawai‘i that may be regained through restoration of lo‘i.
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