Geology topics

Research about Hawaii

Source-linked reports with geographic coverage including Hawaii.

At least 541 records · Page 30Linked to original sources

USGS2015

A sinuous tumulus over an active lava tube at Kīlauea Volcano: evolution, analogs, and hazard forecasts

Inflation of narrow tube-fed basaltic lava flows (tens of meters across), such as those confined by topography, can be focused predominantly along the roof of a lava tube. This can lead to the development of an unusually long tumulus, its shape matching the sinuosity of the underlying lava tube. Such a situation occurred during Kīlauea Volcano's (Hawai'i, USA) ongoing East Rift Zone eruption on a lava tube active from July through November 2010. Short-lived breakouts from the tube buried the flanks of the sinuous, ridge-like tumulus, while the tumulus crest, its surface composed of lava formed very early in the flow's emplacement history, remained poised above the surrounding younger flows. At least several of these breakouts resulted in irrecoverable uplift of the tube roof. Confined sections of the prehistoric Carrizozo and McCartys flows (New Mexico, USA) display similar sinuous, ridge-like features with comparable surface age relationships. We contend that these distinct features formed in a fashion equivalent to that of the sinuous tumulus that formed at Kīlauea in 2010. Moreover, these sinuous tumuli may be analogs for some sinuous ridges evident in orbital images of the Tharsis volcanic province on Mars. The short-lived breakouts from the sinuous tumulus at Kīlauea were caused by surges in discharge through the lava tube, in response to cycles of deflation and inflation (DI events) at Kīlauea's summit. The correlation between DI events and subsequent breakouts aided in lava flow forecasting. Breakouts from the sinuous tumulus advanced repeatedly toward the sparsely populated Kalapana Gardens subdivision, destroying two homes and threatening others. Hazard assessments, including flow occurrence and advance forecasts, were relayed regularly to the Hawai'i County Civil Defense to aid their lava flow hazard mitigation efforts while this lava tube was active.

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USGS2015

Using SO 2 camera imagery and seismicity to examine degassing and gas accumulation at Kīlauea Volcano, May 2010

SO 2 camera measurements at Kīlauea Volcano, Hawaii, in May of 2010 captured two occurrences of lava lake rise and fall within the Halema'um'au Crater summit vent. During high lava stands we observed diminished SO 2 emission rates and decreased seismic tremor. Similar events at Kīlauea have been described as the result of sporadic degassing following gas accumulation beneath a mostly impermeable lava lake surface. Incorporation of SO 2 camera data into a multi-parameter dataset gives credence to the likelihood of shallow gas accumulation as the cause of these high stand events, with accumulated gas release upon lake-level drop compensating for the gas deficit reached during accumulation.

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USGS2015

Steep spatial gradients of volcanic and marine sulfur in Hawaiian rainfall and ecosystems

Sulfur, a nutrient required by terrestrial ecosystems, is likely to be regulated by atmospheric processes in well-drained, upland settings because of its low concentration in most bedrock and generally poor retention by inorganic reactions within soils. Environmental controls on sulfur sources in unpolluted ecosystems have seldom been investigated in detail, even though the possibility of sulfur limiting primary production is much greater where atmospheric deposition of anthropogenic sulfur is low. Here we measure sulfur isotopic compositions of soils, vegetation and bulk atmospheric deposition from the Hawaiian Islands for the purpose of tracing sources of ecosystem sulfur. Hawaiian lava has a mantle-derived sulfur isotopic composition (δ 34 S VCDT) of − 0.8&permil;. Bulk deposition on the island of Maui had a δ 34 S VCDT that varied temporally, spanned a range from + 8.2 to + 19.7&permil;, and reflected isotopic mixing from three sources: sea-salt (+ 21.1&permil;), marine biogenic emissions (+ 15.6&permil;), and volcanic emissions from active vents on Kilauea Volcano (+ 0.8&permil;). A straightforward, weathering-driven transition in ecosystem sulfur sources could be interpreted in the shift from relatively low (0.0 to + 2.7&permil;) to relatively high (+ 17.8 to + 19.3&permil;) soil δ 34 S values along a 0.3 to 4100 ka soil age-gradient, and similar patterns in associated vegetation. However, sub-kilometer scale spatial variation in soil sulfur isotopic composition was found along soil transects assumed by age and mass balance to be dominated by atmospheric sulfur inputs. Soil sulfur isotopic compositions ranged from + 8.1 to + 20.3&permil; and generally decreased with increasing elevation (0–2000 m), distance from the coast (0–12 km), and annual rainfall (180–5000 mm). Such trends reflect the spatial variation in marine versus volcanic inputs from atmospheric deposition. Broadly, these results illustrate how the sources and magnitude of atmospheric deposition can exert controls over ecosystem sulfur biogeochemistry across relatively small spatial scales.

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USGS2015

An analysis of three new infrasound arrays around Kīlauea Volcano

A network of three new infrasound station arrays was installed around Kīlauea Volcano between July 2012 and September 2012, and a preliminary analysis of open-vent monitoring has been completed by Hawaiian Volcano Observatory (HVO). Infrasound is an emerging monitoring method in volcanology that detects perturbations in atmospheric pressure at frequencies below 20 Hz, which can result from volcanic events that are not always observed optically or thermally. Each array has the capability to detect various infrasound events as small as 0.05 Pa as measured at the array site. The infrasound monitoring network capabilities are demonstrated through case studies of rockfalls, pit collapses, and rise-fall cycles at Halema'uma'u Crater and Pu'u 'Ōʻō.

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USGS2015

Satellite monitoring of dramatic changes at Hawai'i's only alpine lake: Lake Waiau on Mauna Kea volcano

Lake Waiau is a small, typically 100-meter-long lake, located near the summit of Mauna Kea volcano, on the Island of Hawaiʻi. It is Hawaiʻi’s only alpine lake and is considered sacred in Hawaiian cultural tradition. Over the past few years, the lake has diminished in size, and, by October 2013, surface water had almost completely disappeared from the lake. In this study, we use high-resolution satellite images and aerial photographs to document recent changes at the lake. Based on our reconstructions covering the past 200 years, the historical lake surface area has typically ranged from 5,000 to 7,000 square meters, but in 2010 a dramatic plunge in lake area ensued. The lake area rebounded significantly in early 2014, following heavy winter storms. This near disappearance of the lake, judging from analysis of visitor photographs and field reports, appears to be highly unusual, if not unprecedented, in the historical record. The unusually low water levels in the lake are consistent with a recent severe drought in Hawaiʻi.

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USGS2015

Groundwater chemistry in the vicinity of the Puna Geothermal Venture Power Plant, Hawai‘i, after two decades of production

We report chemical data for selected shallow wells and coastal springs that were sampled in 2014 to determine whether geothermal power production in the Puna area over the past two decades has affected the characteristics of regional groundwater. The samples were analyzed for major and minor chemical species, trace metals of environmental concern, stable isotopes of water, and two organic compounds (pentane and isopropanol) that are injected into the deep geothermal reservoir at the power plant. Isopropanol was not detected in any of the groundwaters; confirmed detection of pentane was restricted to one monitoring well near the power plant at a low concentration not indicative of source. Thus, neither organic compound linked geothermal operations to groundwater contamination, though chemical stability and transport velocity questions exist for both tracers. Based on our chemical analysis of geothermal fluid at the power plant and on many similar results from commercially analyzed samples, we could not show that geothermal constituents in the groundwaters we sampled came from the commercially developed reservoir. Our data are consistent with a long-held view that heat moves by conduction from the geothermal reservoir into shallow groundwaters through a zone of low permeability rock that blocks passage of geothermal water. The data do not rule out all impacts of geothermal production on groundwater. Removal of heat during production, for example, may be responsible for minor changes that have occurred in some groundwater over time, such as the decline in temperature of one monitoring well near the power plant. Such indirect impacts are much harder to assess, but point out the need for an ongoing groundwater monitoring program that should include the coastal springs down-gradient from the power plant.

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USGS2015

Dim ultraviolet light as a means of deterring activity by the Hawaiian hoary bat Lasiurus cinereus semotus

Widespread bat fatalities at industrial wind turbines are a conservation issue with the potential to inhibit efficient use of an abundant source of energy. Bat fatalities can be reduced by altering turbine operations, but such curtailment decreases turbine efficiency. If additional ways of reducing bat fatalities at wind turbines were available such tradeoffs might not be needed. Based on the facts that bats perceive distant objects primarily through vision and can see in very dim lighting conditions, and the possibility that bats might interact with turbines after approaching them as they would trees, we propose a novel method of reducing bat activity at wind turbines: illumination of the structure with dim light. As a first step toward assessing this approach, we illuminated trees with dim flickering ultraviolet (UV) light in areas frequented by Hawaiian hoary bats Lasiurus cinereus semotus , an endangered subspecies affected by wind turbines. We used a repeated-measures design to quantify bat activity near trees with acoustic detectors and thermal video cameras in the presence and absence of UV illumination, while concurrently monitoring insect numbers. Results indicate that dim UV reduces bat activity despite an increase in insect numbers. Experimental treatment did not completely inhibit bat activity near trees, nor did all measures of bat activity show statistically significant differences due to high variance in bat activity among sites. However, the observed decreases in bat activity with dim UV illumination justify further testing of this method as a means to reduce bat fatalities at wind turbines.

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USGS2015

Evaluating the piscicide rotenone as an option for eradication of invasive Mozambique tilapia in a Hawaiian brackish-water wetland complex

Mozambique tilapia Oreochromis mossambicus were recently discovered in ‘Aimakapā Fishpond, a 12-hectare brackish-water wetland complex in Kaloko-Honokōhau National Historical Park, on the Island of Hawai’i. As a possible eradication method, we evaluated rotenone, a natural piscicide used in fish management and the active ingredient in plants traditionally used by indigenous Hawaiians for capturing fish. To assess rotenone’s efficacy in killing tilapia and effects on non-target species, laboratory toxicity tests involved exposing organisms to various concentrations of liquid CFT Legumine (5% rotenone) in static trials of 48-h to 72-h duration. Test organisms included: Mozambique tilapia, non-native guppy Poecilia reticulata , the non-native odonate Rambur’s forktail Ischnura ramburii , native feeble shrimp Palaemon debilis , and native ‘ōpae’ula shrimp Halocaridina rubra . All organisms and water used in tests were obtained from ‘Aimakapā (12.6–12.7 ppt salinity), or, for H. rubra , an anchialine pool (15.0–15.2 ppt salinity). Survival analyses indicated CFT Legumine concentrations >3 ppm (>0.15 mg/L rotenone) achieved 100% mortality of tilapia and 93% of guppies within 24 h, with most tilapia killed by 6 h and most guppies by 2 h. Little or no mortality was observed among invertebrate exposed to 1 to 5 mg/L CFT Legumine: 0% mortality for ‘ōpae’ula shrimp, 4% for feeble shrimp; and 16% for odonate larvae. The 48 h LC50 values for Mozambique tilapia and guppy were 0.06 and 0.11 mg/L rotenone, respectively. Results demonstrate rotenone’s potential for non-native fish eradication in brackish-water habitats, with benefit of low mortality to certain macro-invertebrates. High rotenone tolerance displayed by ‘ōpae’ula shrimp is noteworthy. Invasive fish are common in anchialine pools, threatening existence of shrimp and other invertebrate fauna. Although rotenone’s effects on freshwater organisms have been well studied, our research represents one of only a few controlled laboratory experiments quantitatively assessing rotenone tolerance of brackish or marine fauna.

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USGS2015

Mortality patterns in endangered Hawaiian geese (Nene; Branta sandvicensis )

Understanding causes of death can aid management and recovery of endangered bird populations. Toward those ends, we systematically examined 300 carcasses of endangered Hawaiian Geese (Nene; Branta sandvicensis ) from Hawaii, Maui, Molokai, and Kauai between 1992 and 2013. The most common cause of death was emaciation, followed by trauma (vehicular strikes and predation), and infectious/inflammatory diseases of which toxoplasmosis (infection with Toxoplasma gondii ) predominated. Toxicoses were less common and were dominated by lead poisoning or botulism. For captive birds, inflammatory conditions predominated, whereas emaciation, trauma, and inflammation were common in free-ranging birds. Mortality patterns were similar for males and females. Trauma predominated for adults, whereas emaciation was more common for goslings. Causes of death varied among islands, with trauma dominating on Molokai, emaciation and inflammation on Kauai, emaciation on Hawaii, and inflammation and trauma on Maui. Understanding habitat or genetic-related factors that predispose Nene (particularly goslings) to emaciation might reduce the impact of this finding. In addition, trauma and infection with T. gondii are human-related problems that may be attenuated if effectively managed (e.g., road signs, enforcement of speed limits, feral cat [ Felis catus ] control). Such management actions might serve to enhance recovery of this endangered species.

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USGS2015

Primative components, crustal assimilation, and magmatic degassing of the 2008 Kilauea summit eruption

Simultaneous summit and rift zone eruptions at Kīlauea starting in 2008 reflect a shallow eruptive plumbing system inundated by a bourgeoning supply of new magma from depth. Olivine-hosted melt inclusions, host glass, and bulk lava compositions of magma erupted at both the summit and east rift zone demonstrate chemical continuity at both ends of a well-worn summit-to-rift pipeline. Analysis of glass within dense-cored lapilli erupted from the summit in March – August 2008 show these are not samplings of compositionally distinct magmas stored in the shallow summit magma reservoir, but instead result from remelting and assimilation of fragments from conduit wall and vent blocks. Summit pyroclasts show the predominant and most primitive component erupted to be a homogenous, relatively trace-element-depleted melt that is a compositionally indistinguishable from east rift lava. Based on a “top-down” model for the geochemical variation in east rift zone lava over the past 30 years, we suggest that the apparent absence of a 1982 enriched component in melt inclusions, as well as the proposed summit-rift zone connectivity based on sulfur and mineral chemistry, indicate that the last of the pre-1983 magma has been flushed out of the summit reservoir during the surge of mantle-derived magma from 2003-2007.

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USGS2015

Evidence of low genetic variation and rare alleles in a bottlenecked endangered island endemic, the Lasan Teal (Anas laysanensis)

Genetic diversity is assumed to reflect the evolutionary potential and adaptability of populations, and thus quantifying the genetic diversity of endangered species is useful for recovery programs. In particular, if conservation strategies include reintroductions, periodic genetic assessments are useful to evaluate whether management efforts have resulted in the maximization or loss of genetic variation within populations over generations. In this study, we collected blood, feather, and tissue samples during 1999–2009 and quantified genetic diversity for a critically endangered waterfowl species endemic to the Hawaiian archipelago, the Laysan teal or duck (Anas laysanensis; n = 239 individual birds sampled). The last extant population of this species at Laysan Island was sourced in 2004–2005 for a ‘wild to wild’ translocation of 42 individuals for an experimental reintroduction to Midway Atoll. To inform future management strategies, we compared genetic diversity sampled from the source population (n = 133 Laysan birds) including 23 of Midway’s founders and offspring of the translocated population 2–5 years post release (n = 96 Midway birds). We attempted to identify polymorphic markers by screening nuclear microsatellite (N = 83) and intronic loci (N = 19), as well as the mitochondrial control region (mtDNA) for a subset of samples. Among 83 microsatellite loci screened, six were variable. We found low nuclear variation consistent with the species’ historical population bottlenecks and sequence variation was observed at a single intron locus. We detected no variation within the mtDNA. We found limited but similar estimates of allelic richness (2.58 alleles per locus) and heterozygosity within islands. Two rare alleles found in the Laysan Island source population were not present in the Midway translocated group, and a rare allele was discovered in an individual on Midway in 2008. We found similar genetic diversity and low, but statistically significant, levels of differentiation (0.6%) between island populations suggesting that genetic drift (as a result of translocation-induced population bottlenecking) has had a limited effect within five years post-release. Our results have utility for informing translocation and genetic management decisions.

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USGS2015

Vegetation and non-native ungulate monitoring at the Big Island National Wildlife Refuge Complex 2010–2014.

The Hakalau Forest Unit (HFU) of Big Island National Wildlife Refuge Complex (BINWRC) has intensively managed feral cattle (Bos taurus) and pigs (Sus scrofa) and monitored non-native ungulate presence and distribution during surveys of all managed areas since 1988. We: 1) provide results from recent ungulate surveys at HFU to determine current feral pig abundance and distribution; 2) present results of surveys of ungulate presence and distribution at the Kona Forest Unit (KFU); 3) present results of surveys of weed presence and cover at both refuge units; and 4) present baseline results from long-term vegetation monitoring plots at KFU. Overall pig abundance appears to have decreased at HFU, although not significantly, over the period from 2010 to 2014. Management units 2 and 4 contained the majority of pigs at HFU. Pig density outside of adjacent managed areas has declined significantly from 2010 to 2014 for unknown reasons. Ungulate sign occurred in > 50% of plots at KFU during the November 2012 and September 2013 surveys, but ungulate sign occurred in < 28% of plots during three other surveys. The ability to differentiate sign of ungulate species remains problematic at KFU. Changes in weed cover do not yet demonstrate any strong temporal pattern. Spatial patterns are more pronounced; however, some weed species may not be reliably represented due to observers’ abilities to recognize less common weeds. Nonetheless, the distribution and cover of fireweed (Senecio madagascariensis) at KFU may have increased over the study period. Vegetation surveys documented baseline floristic composition and forest structure at KFU. It is not known if this current amount of emerging cover is sufficient for long-term self-sustaining forest canopy regeneration; however, numerous ‘ōhi‘a seedlings were found in the wet forest and mesic ‘ōhi‘a habitats, indicating an ample viable seed source and robust potential for forest regeneration.

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USGS2015

Farallon de Medinilla seabird and Tinian moorhen analyses

This report assesses the trends in brown booby (Sula leucogaster), masked booby (S. dactylatra), and red-footed booby (S. sula) counts collected on Farallon de Medinilla and Mariana common moorhen (Gallinula chloropus guami) counts on Tinian, Commonwealth of the Northern Mariana Islands to help elucidate patterns in bird numbers. During either monthly or quarterly surveys between 1997 and 2014 counts of all four bird species were recorded, generating a relatively noisy time series revealing inter-annual variation in index counts by as much as 1,000%. For the purposes of assessing long-term population trends across years we chose a single, species-specific month to assess trends. Doing so reduces the effect of intra-annual variation allowing the analysis to focus on inter-annual variation important to long-term trends assessment. There are clear fluctuations in the counts of all four species. Although the trends were non-significant, there is some evidence that masked and red-footed booby species have declined while brown booby and moorhen have increased.

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USGS2015

An assessment of arthropod prey resources at Nakula Natural Area Reserve, a potential site of reintroduction for Kiwikiu (Pseudonestor xanthophrys) and Maui `Alauahio (Parareomyza montana)

Hawaiian forest birds have declined dramatically since humans arrived in the archipelago. Birds from all foraging guilds have been affected but insectivorous species are currently at greatest risk of extinction. On the island of Maui, populations and ranges of the insectivorous kiwikiu (Maui parrotbill; Pseudonestor xanthophrys) and Maui ‘alauahio (Maui creeper; Paroreomyza montana) have declined significantly from historic levels primarily due to habitat loss, predation,disease, and food web disruption, leading to federal listings of endangered species and species of concern, respectively. Recovery plans for these birds include reestablishment of populations in parts of their former range. Nakula Natural Area Reserve on the leeward side of HaleakalāVolcano has been targeted for release of wild-caught or captive-bred individuals. The mesic, montane koa-‘ōhi‘a (Acacia koa-Metrosideros polymorpha) forest at Nakula has been heavily impacted through grazing by feral ungulates, but recent management actions to exclude these animals are promoting forest recovery. The objective of this study was to assess the arthropod prey base at Nakula in preparation for reintroductions of kiwikiu and Maui ‘alauahio. To accomplish that goal, we compared arthropod abundances at Nakula to those at Hanawi Natural Area Reserve and Waikamoi Preserve, areas where kiwikiu and Maui ‘alauahio are currently found. We also identified diets of kiwikiu and Maui ‘alauahio from fecal samples to better understand and evaluate the prey base at Nakula. Assessment methods included clipping branch tips to sample arthropods within the foliage of koa and ‘ōhi‘a, using traps to quantify arthropods on koa and ‘ōhi‘a bark surfaces, counting exit holes to quantify abundances of beetles (Coleoptera) within dead branches of koa, and measuring the density of arthropods within the stems of ‘ākala (Rubus hawaiiensis). The diet of kiwikiu was dominated by caterpillars (Lepidoptera larvae), which comprised 90% of all prey items for 50 adult birds and 98% of all prey for two nestlings. Caterpillars were also the most important prey for Maui ‘alauahio (43% for 104 adult birds) although spiders (Araneae, 16%), beetles (12%) and true bugs, planthoppers and psyllids (Hemiptera; 12%) were also important. Caterpillars were generally the most abundant type of arthropod in the foliage of koa and ‘ōhi‘a, although spiders, beetles and hemipterans were also common. Total arthropod biomass and caterpillar biomass at Nakula was as great, or greater, than that observed at Hanawi and Waikamoi per unit of foliage of both koa and ‘ōhi‘a. Spiders generally dominated the bark fauna on both koa and ‘ōhi‘a at all sites although isopods (Isopoda), millipedes (Myriapoda: Millipeda) and lacewings (Neuroptera) were also abundant at Waikamoi and Hanawi. Total arthropod biomass on bark, as well as the biomass of several individual taxa, was significantly lower at Nakula than the other sites. Our measurement of the density of beetle exit holes in dead koa branches found no difference between Nakula and Waikamoi. Finally, no difference existed in the abundance of arthropods (primarily caterpillars and moth pupae) within ‘ākala stems among sites. With the exception of bark surfaces, our results suggest that the arthropod prey base for birds on primary foraging substrates at Nakula is similar to that found at two sites within the current range of kiwikiu and Maui ‘alauahio. However, our results should be viewed with caution because they are limited to the scale of individual branch, tree, or ‘ākala stem. To complete the assessment, our results should be scaled up to the landscape level by determining the density of each substrate within each site. Key arthropod prey of kiwikiu and Maui ‘alauahio are available at Nakula and, as habitat restoration continues, food abundance should increase to the point at which populations of these birds can be supported.

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USGS2015

Palila Restoration Research, 1996−2012. Summary and management implications

The Palila Restoration Project was initiated in 1996 by the U.S. Geological Survey to assist government agencies mitigate the effects of realigning Saddle Road (Highway 200) through Palila Critical Habitat (U.S. Fish and Wildlife Service 1998, Federal Highway Administration 1999). Ecological research on the palila (Loxioides bailleui), an endangered Hawaiian forest bird, carried out by the U.S. Geological Survey (formerly organized as the Research Division of U.S. Fish and Wildlife Service) since 1987 and research conducted by the Palila Restoration Project provided the scientific bases for developing a recovery strategy (U.S. Fish and Wildlife Service 2006) and its adaptive implementation. The main objectives of the Palila Restoration Project were to develop techniques for reintroducing the palila to a portion of its former range, investigate the biological threats to the palila and its habitat, and synthesize the existing body of ecological knowledge concerning the palila. Five broad study themes formed the research framework: 1. Population reintroduction and restoration 2. Demography and breeding ecology 3. Habitat use and food ecology 4. Vegetation ecology 5. Predator ecology and management An element that was not included in the research program of the project was the ecology and management of introduced ungulates, which has historically constituted the single greatest threat to Palila Critical Habitat (Banko et al. 2009). The absence of ungulate studies should not be interpreted to mean that we believe ungulates no longer damage palila habitat. Other research has already established that removing alien browsers and grazers from Mauna Kea is essential for the recovery of the subalpine forest on which palila now depend (Scowcroft and Giffin 1983; Scowcroft and Sakai 1983; Scowcroft and Conrad 1988, 1992; Hess et al. 1999). Moreover, the Federal District Court of Hawai‘i has ordered the State of Hawai‘i to remove browsing ungulates from Palila Critical Habitat (Banko et al. 2009, Hess and Banko 2011). This final report summarizes results of Palila Restoration Project research from December 1996 to December 2012. Even though some results contained in this report have been published in scientific journals and other technical reports (Appendix I), they are included here to provide a comprehensive chronicle of all project activities.

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USGS2015

Behavior of the Hawaiian Hawaiian Hoary Bat (Lasiurus cinereus semotus) at wind turbines and its distribution across the North Ko'olau Mountains, O'ahu

We studied the landscape distribution of endemic Hawaiian hoary bats (Lasiurus cinereus semotus ) on the north Ko‘olau Mountains of O‘ahu, Hawai‘i, from May 2013 to May 2014, while simultaneously studying their behavior at wind turbines within the broader landscape. This research aimed to assess the risk that wind turbines pose to bats on the island and integrated a variety of methods, including acoustic monitoring, thermal videography, and fatality searches.Our findings indicate that hoary bats were acoustically cryptic and occurred sparsely in the region. Overall site occupancy rate was 55% during the 1-year period of acoustic monitoring at 23 sites, and there was only an 8% chance of acoustically detecting a bat on a given night if it was present. We detected bats less frequently in windward northern parts of the study area and at windy, lower-elevation sites with rough terrain. Bats were detected more frequently in leeward southern parts of the study area and at wind-sheltered, higher-elevation sites with flat ridgetops. Acoustic detections were consistently low from October through February and increased at most sites to peak in April through August. However, meteorological conditions were not found to be associated with the acoustic prevalence of bats on a night-to-night basis. We observed more than three thousand events involving bats during six months of nightly video surveillance at four wind turbines. Video monitoring revealed several links to weather at the local scale, despite acoustic detections not clearly relating to weather in our broader landscape analysis. Video demonstrated bats occurring near turbines more often on nights with little rain, warmer temperatures, moderate wind speeds, low humidity, and the low but rising barometric pressures indicative of fair weather and improved foraging conditions. Video monitoring also demonstrated that the presence of bats near turbines strongly correlates with insect presence. We detected bats on video rather infrequently, averaging only one to two passes per hour. Most detections were brief (median = 4.0 sec) and involved single bats (97%), with the amount of time during which bats were observed totaling to only 0.10% of the video analyzed (about 3.8 hours of 3,847 total hours). Bats frequently foraged in the airspace near turbines. These results differ from a recent similar study on the mainland (continental North America) and may indicate that Hawaiian hoary bats spend less time closely approaching wind turbines and show less interest in them than their more-migratory mainland conspecifics. We speculate that the Hawaiian hoary bats we observed were locally resident and frequenting high-quality habitat near familiar structures. In contrast, hoary bats observed at wind facilities on the mainland appear to approach and investigate unfamiliar landscape structures that they mistake for trees as they migrate long distances. Consequently, Hawaiian hoary bats may be less susceptible to fatality at wind turbines on a per-encounter basis than hoary bats in North America. Only one bat carcass was found at the four turbines searched daily for six months. The relatively high probability of finding carcasses provided strong assurance that few carcasses were likely missed—there was less than a 10% chance that total fatality at the four turbines monitored for half a year exceeded three bats.

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USGS2015

Efforts to eradicate yellow crazy ants on Johnston Atoll: Results from Crazy Ant Strike Team IX, December 2014-June 2015

The ecologically destructive yellow crazy ant (YCA; Anoplolepis gracilipes ) was first detected on Johnston Atoll in January 2010. Within eight months, the U.S. Fish and Wildlife Service had mobilized its first crazy ant strike team (CAST), a group of biologists dedicated to testing and identifying insecticidal baits to be used to eradicate the ant on the atoll. During December 2014‒May 2015 CAST IX focused on testing hydrogel crystals saturated with sucrose solution (25%) carrying the insecticides thiamethoxam and dinotefuran against YCA. A series of experiments, including artificial nest box trials, and field-based palatability trials and eradication tests on small (500 m2 or 0.05 ha) and large plots (2500 m2 or 0.25 ha), were conducted to test concentrations of thiamethoxam ranging from 0.0005% to 0.01%, and dinotefuran at 0.05%. Additionally, the cat food-based matrix containing dinotefuran (0.05%), the standard bait used to suppress YCA on Johnston since 2011, and textured vegetable protein (TVP) carrying dinotefuran at 0.1% and 0.05% were included in large plot tests. Nest box trials were inconclusive due to a consistent loss of queen and worker ants in control boxes, so they were discontinued. Palatability trials suggested higher dosages of thiamethoxam (0.005 and 0.01%) were less attractive than lower dosages (0.0005 and 0.001%) and controls (sucrose only), but small and large plot experiments failed to identify a thiamethoxam concentration that was consistently effective at killing YCA. In contrast, hydrogel containing dinotefuran was consistently effective, killing >95% of YCA on small and large plots. As expected, the cat food bait effectively reduced YCA abundances, but was slightly less effective than hydrogel containing dinotefuran over time. Three successive, approximately weekly treatments of large plots with hydrogel bait, or other baits followed by hydrogel bait, suggest an increasing overall effectiveness, with no aversion of YCA to the bait. This finding is important in that it indicates that hydrogel bait can be applied at short time intervals, potentially resulting in relatively constant exposure of YCA to highly attractive, yet toxic, sucrose-based bait. TVP performed similar to hydrogel, reducing YCA abundance >92% at both concentrations tested. Finally, dosages of hydrogel containing dinotefuran at 6, 12 and 24 l/0.25 ha were all effective at reducing YCA on large plots. Overall, results from these experiments suggest that hydrogel containing dinotefuran (0.05%) is a promising tool for eradicating YCA on Johnston Atoll.

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USGS2015

Richness, diversity, and similarity of arthropod prey consumed by a community of Hawaiian forest birds.

We evaluated the diet richness, diversity, and similarity of a community of seven endemic and two introduced passerine birds by analyzing the composition of arthropod prey in fecal samples collected during 1994–1998 at Hakalau Forest National Wildlife Refuge, Hawai‘i Island. Most prey fragments were identified to order, but we also distinguished among morpho-species of Lepidoptera based on the shape of larval (caterpillar) mandibles for higher resolution of this important prey type. Diets were compared among feeding specialists, generalists, and “intermediate” species and among introduced and three endangered Hawaiian honeycreeper (Fringillidae) species. Lepidoptera (moths), especially the larval (caterpillar) stage, comprised the greatest proportion of prey in samples of all bird species except for the introduced Japanese white-eye ( Zosterops japonicus ; JAWE). Araneae (spiders) was the most abundant order in JAWE samples and the second most abundant order for most other species. The two specialist honeycreepers ranked lowest in the richness and diversity of arthropod orders, but only the ‘akiapōlā‘au ( Hemignathus munroi , AKIP) was significantly lower than the three generalist or intermediate honeycreeper species. The diversity of arthropod orders was significantly lower for the three endangered honeycreeper species compared to the two introduced species. No significant differences were observed among the five honeycreepers with respect to the arthropod orders they consumed. The use of arthropod orders taken by endangered honeycreepers and introduced species was significantly different in all paired comparisons except for JAWE and ‘ākepa ( Loxops coccineus ; AKEP). In terms of richness and diversity of caterpillar morpho-species in the diet, only the specialist, AKEP, was significantly lower than all three generalist and intermediate species. Both AKEP and AKIP consumed a significantly different diet of caterpillar morpho-species compared to at least one honeycreeper generalist or intermediate species. Among the endangered honeycreepers and introduced species, the richness and diversity of caterpillar morpho-species was significantly lower only for AKEP compared to both introduced species. Significant differences were not observed between endangered and introduced species in the distribution of caterpillar morpho-species in the diet. Only three morpho-species were heavily exploited, with one being consumed by all bird species. The heavy exploitation of very few morpho-species by specialists underscored their greater vulnerability to changes in forest food webs and threats to key arthropod prey. When evaluated together with data on overlap in foraging behavior, our results could be useful in evaluating competition between bird species at Hakalau. Nevertheless, invasive parasitoid wasps may impact key caterpillar prey more substantially than do introduced birds, highlighting the need for additional research to understand the ecology of caterpillar species and their interactions with both invertebrate and vertebrate consumers. The severe decline of specialist bird species historically and recently is a reminder of the importance of maintaining food web resilience, potentially through vigorous habitat restoration, to withstand the continuing and perhaps increasing threats from a diverse array of invasive species and climate change.

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