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Long‐term ecological studies are invaluable for detecting changes over time. Forest restoration has been a conservation priority in Hawaiʻi, where invasive species have negatively impacted native bird habitat. During 1993–1994, a study was conducted of Hawaiʻi ʻelepaio (Chasiempis sandwichensis) nest site selection and forest composition in mesic montane forest along Mauna Loa Road in Hawaiʻi Volcanoes National Park. We returned to the site and repeated the methods used in the earlier study to record Hawaiʻi ʻelepaio nest site selection (tree species, tree and nest height, and tree girth [diameter at breast height, DBH]) from 2015 to 2017, and measured forest composition (tree density, relative abundance, height, and DBH) in 2019. Three times as many nests were found in ʻaʻaliʻi (Dodonaea viscosa) as in koa (Acacia koa) in both time periods. Heights of koa and ʻaʻaliʻi did not change, but their DBH increased over time. The relative height of nests in ʻaʻaliʻi trees did not change, but nests in koa were placed higher in the crown during the later study. Overall tree density increased from 1,619 (95% confidence interval [CI] = 1,499–1,740) trees/ha to 2,583 (95% CI = 2,176–3,096) trees/ha. Koa relative abundance was 53% of total trees earlier and 45% later, ʻaʻaliʻi remained at 47%, and māmane (Sophora chrysophylla) increased from 0 to 8% over time. Our results indicate that changes in forest composition affect nesting behavior, but in ways that are not necessarily simple or consistent. [ABSTRACT FROM AUTHOR]

Invasive fish can profoundly affect communities they invade. In Hawai'i, invasive fishes have become established in many anchialine pools, threatening the persistence of resident invertebrates, including several endangered species. Tools to eradicate invasive fishes from these pools are lacking. This study tested the efficacy of carbon dioxide (CO2) gas diffused into anchialine pool water as a method to eradicate invasive Mozambique tilapia (Oreochromis mossambicus), guppies (Poecilia reticulata), and western mosquitofish (Gambusia affinis). We first conducted aquarium trials to identify how these fishes were affected by elevated CO2 and the concomitant reduction in pH. We then carried out field trials in pools containing these fish in one pool each at two national historical parks on the Island of Hawai'i during July 2021-January 2022. We also developed environmental DNA (eDNA) protocols to detect fish that may have survived CO2 treatments. The effect of CO2 on fish behavior varied among species; at pH 5.3 (CO2 = 255 mg/L) for tilapia and 5.0 (CO2 = 488 mg/L) for tilapia, guppies, and mosquitofish, all generally lost their ability to swim, showed slow or no gill movement, and altered their position in the water column. No tilapia survived the trials (n = 4 and 6 individuals at pH 5.3 and 5.0, respectively). In contrast, 41.7% (n = 12) of adult guppies and 66.7% (n = 12) of adult mosquitofish survived treatment at pH 5.0. In the field we were unable to reduce anchialine pool water pH below 5.7. Regardless, we were able to eradicate tilapia from one pool over four sequential treatments. Post-treatment eDNA assessments supported visual surveys, confirming our results. We were not able to eradicate guppies and mosquitofish. Results from this study show that CO2 can be an effective tool for eradicating invasive tilapia from anchialine pools, and post-treatment eDNA assessments can provide managers with a method for evaluating the success of eradication efforts. [ABSTRACT FROM AUTHOR]

Introduced predators are one of the most important limiting factors for endemic Hawaiian forest birds. In the sub­alpine zone of Mauna Kea on the island of Hawaii, the primary predators of the endangered Hawaiian finch, palila (Loxioides bailleui), are feral house cats. Remote video monitoring revealed that feral cats are primarily diurnal predators of palila during the extended period of nestling development. Reducing this predation is necessary for population recovery and efforts to reintroduce palila to parts of their historical range. Currently, feral cats are removed with an extensive array of live traps. Since 1998, 7,344 trap nights of effort have been implemented, and although temporary declines in capture occur within seasons, cumulative capture rates show there has been little lasting effect from season to season. New emphases on improving capture efficiency include improved techniques for attracting cats to traps with lures that require infrequent refreshing or maintenance, “smart trap” technology that efficiently notifies managers when traps of all types contain animals, and adaptive strategies for managing feral cat populations in a variety of habitats and parks in the Pacific. Further documentation and interpretation of feral cat impacts on native wildlife will help prioritize and justify requests for increased funding for predator management. Accurate information on feral cat problems will help educate decision-makers and the public of the need for increased funding to protect endangered birds from this threat.

Effective species management and conservation require knowledge of species distribution and status. We used point‐transect distance sampling surveys of the endangered palila (Loxioides bailleui), a honeycreeper currently found only on the Island of Hawai'i, USA, to generate robust estimates of total abundance and simultaneously model the distribution, abundance, and spatial correlation of the species as a density surface model (DSM). Point‐transect distance sampling is a widely applied method to estimate bird densities accounting for imperfect detection probability. For the DSM we used a generalized additive model framework and soap film smoothers to control the effects of boundary features. This modeling approach allowed us to account for imperfect detection and propagate detection probability uncertainty. We compared the uncertainty in palila abundance estimates using standard point‐transect distance sampling to estimates from the DSM. The DSM, accounting for both distance‐sampling‐derived detection probability variance and the generalized additive model density estimate variance, did not improve population estimator precision; however, it provided insight into the species' distribution, density, and uncertainty. We also applied excursion sets analysis to objectively identify areas where the species occurs in high densities. The 2017 global population of <2,000 individuals was limited to an excursion area of 1,500 ha. Our findings can help management and regulatory agencies by simultaneously mapping a species' distribution and density, improving survey protocols, and providing information important to species conservation. [ABSTRACT FROM AUTHOR]

Feral cats (Felis catus) have spread throughout anthropogenic and insular environments of the world. They now threaten many species of native wildlife with chronic depredation. Knowledge of feral cat population dynamics is necessary to understand their ecological effects and to develop effective control strategies. However, there are few studies worldwide regarding annual or lifetime survival rates in remote systems, and none on Pacific islands. We constructed the age distribution and estimated survival of feral cats in a remote area of Hawai'i Island using cementum lines present in lower canine teeth. Our data suggest annual cementum line formation. A log-linear model estimated annual survival ≥ 1 yr of age to be 0.647. Relatively high survival coupled with high reproductive output allows individual cats to affect native wildlife for many years and cat populations to rebound quickly after control efforts., Feral cats (Felis catus) are considered by the World Conservation Union (IUCN) as one of the '100 of the world's worst invasive alien species' (Lowe et al. 2000). They have [...]

The endangered palila (Loxioides bailleui) is a flagship species of Hawaiian forest bird conservation. Due mainly to long-term ecological research by U.S. Geological Survey (USGS) biologists and many hundreds of [...]