Nesting Time Impacts on 'Ae'o Nest Depredation |
In this study 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.
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Water Diversion: Assessing Optimal Flow for Sustaining Populations of the Endangered Hawaiian Stilt |
In 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 species. 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 Waterbirds |
Conventional 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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Avian Presence, Restoration, and Indigenous Agriculture |
Approximately 15% of wetlands have been lost across Hawai‘i since the industrial era, with ~44% of the total loss occurring in coastal areas, contributing to the listing of Hawaiian waterbird species as Endangered. However, the height of historical waterbird populations corresponded with the height of Hawaiian social-ecological systems due to the ability of indigenous flooded-field systems (lo`i) to provide foraging and nesting habitat. This study aims to understand the relationship between waterbird life cycles and management cycles within the agro-ecosystem as a means to assess the potential of lo‘i restoration to contribute to waterbird recovery. Observations in 2019 revealed 'ae'o (Himantopus mexicanus knudseni) and 'alae 'ula (Gallinula galeata sandvicensis), both disturbance-adapted species, partitioned the lo`i habitat temporally and spatially according to managed succession within the agro-ecosystem, which mimics the disturbance regimes these waterbirds evolved in. Results from this study are important for informing management decisions regarding both loʻi kalo and waterbird populations and may help influence policies that allow waterbird populations to once again thrive alongside human populations.
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(re)Establishing pilina: Understanding the relationship between communities and ‘alae ‘ula
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Climate change is expected to decrease current habitat for the endangered ‘alae ‘ula (Hawaiian Gallinule; Gallinula galeata sandvicensis) in coastal wetlands by at least 40%. However, the pae ‘āina (main 8 Hawaiian Islands) is experiencing a revitalization of Indigenous agro-ecological practices of loʻi (flooded agriculture) and loko i‘a (fishponds), which historically expanded wetland habitat, and thus has the potential to expand habitat for the ‘alae ‘ula. Under the federal Endangered Species Act (ESA), human interactions with endangered species are restricted due to the possible negative effects of human disturbance on behavior. Thus, farming practices may be impacted when ‘alae ‘ula nest in loʻi. If these interactions do result in nest abandonment or other impacts to nesting success, then the restrictions imposed on farmers under the ESA are necessary to help recover the species. However, recent observations suggest ‘alae ‘ula may recognize individual farmers with whom they regularly interact in loʻi, and furthermore, that reproductive success is not impacted by interactions with these farmers with whom they have formed relationships.
The objective of this study is to understand the pilina, or relationship, between ʻalae ʻula and kalo farmers. We will determine: (1) whether ʻalae ʻula are able to identify individual humans;(2) the baseline kinship that farmers believe they have with ʻalae ʻula that inhabit their loʻi. |
Juvenile 'Ae'o Survival and Habitat Use |
'Ae'o are endangered in the Hawaiian Islands, and their success is negatively affected by invasive predators and continued habitat loss. Juvenile 'ae'o, particularly those 0 - 10 days old are most vulnerable to death due to predation or exposure (starvation, exhaustion, contamination, abandonment). This project was created to assess the survival of 'ae'o juveniles in a dynamic wetland system at the Marine Corps Base Hawai'i - Kāne'ohe Bay, and to determine the habitat characteristics, if any, that promote successful reproduction. 'Ae'o nests will be monitored to determine hatching success, and juveniles captured at 7 - 10 days old and outfitted with individualized color bands and a radio transmitter. Juveniles will be tracked until fledging to determine fate and habitat use. Preliminary results indicate that many juveniles do not survive to 10 days old, and those that fledge typically have home ranges of 0.94 ± 0.39 acres that are in close proximity to the original nest site. Therefore, site managers of areas with nesting 'ae'o should employ predator control methods to reduce predator pressure from invasive mammalian predators, and preserve or create habitat that reduces the risk of exposure.
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