Geology topics

Richard J. Camp

Publications and source records attributed to Richard J. Camp.

At least 73 records · Page 4Linked to original sources

USGS2017

Pacific Island landbird monitoring report, Hawaiʻi Volcanoes National Park, 2015-2016: Tract groups 1 and 2

Hawaiʻi Volcanoes National Park (HAVO) was surveyed for landbirds and landbird habitat from February through April 2015 and February through April 2016. This information provides the second datum in the time-series of Pacific Island Network (PACN) monitoring for long-term trends in landbird distribution, density, and abundance. Initial PACN surveys were conducted in 2010 and are repeated every five years. The entire survey area was comprised of eight tracts in forest, woodland, and shrub habitat, totaling 26,364 ha. Each tract was surveyed using point-transect distance sampling to calculate estimates of bird abundance and density. In addition to the permanent PACN survey transects, randomly generated point-transects were also surveyed, allowing for a split panel sampling design. A total of 14,061 bird detections of twenty-eight species were recorded during point counts; 8 species were native to Hawaiʻi and 20 species were non-native. ʻApapane (Himatione sanguinea) and Hawaiʻi ‘Amakihi (Chlorodrepanis virens virens) were the most abundant and widely distributed native species detected. ‘Ōma’o (Myadestes obscurus), ‘I‘iwi (Drepanis coccinea), and Hawaiʻi Elepaio (Chasiempis sandwichensis) occurred at fewer than 30% of the 757 stations surveyed, and were absent from some tracts. Three species of native birds detected during surveys were endangered—ʻIo (Buteo solitarius), Hawaiʻi Creeper (Loxops mana), and Hawaiʻi ʻAkepa (Loxops coccineus). Two additional endangered species were detected incidentally on transects—Nēnē (Branta sandwicensis) and ʻAkiapolaʻau (Hemignathus wilsoni). Non-native Japanese White-eye (Zosterops japonicus), Northern Cardinal (Cardinalis cardinalis), Japanese Bush Warbler (Horomis diphone), and Yellow-fronted Canary (Crithagra mozambica) were detected throughout most tracts and had the highest relative abundances among non-natives. The remaining species detected occurred at less than 10% of stations surveyed. Sufficient detections to allow density estimation were made for 11 species (5 native and 6 non-native). Changes in species-specific densities by tract were assessed between the initial and current surveys using two-sample z-tests in an equivalence testing framework to determine long-term trends. Differences between densities were highly variable for native species; including increasing, decreasing and stable trends. There were notable increases of ‘I‘iwi and ‘Ōma’o densities in some tracts. However there were also declines of ‘Ōma’o in three tracts, including leeward Northwest Kahuku where birds were detected in 2010 for the first time in over 30 years, but not during this recent survey. ‘I‘iwi densities increased in the high elevation Pāpā tract; however, they declined in the Mauna Loa Strip tract where the species may be vulnerable to avian malaria. Trend results for Hawaiʻi ʻAkepa were inconclusive, but the species occurred at more survey stations than in 2010, and we estimate a density of 0.31 ±0.34 birds/ha in the 10,989 ha Kahuku tract. Hawaiʻi Creeper had in an increasing trend in the Kahuku tract with a density of 0.16 ± 0.07 birds/ha and an inconclusive trend in Honomalino, where there was only one detection in 2016. There was a large expansion in the distribution and abundance of the non-native Yellow-fronted Canary and Japanese Bush Warbler. The Lavender Waxbill (Estrilda caerulescens) was detected in HAVO for the first time. Trend results were variable for other non-native species, but generally maintained stable densities when compared to previous landbird surveys. Several habitat variables were sampled at monitoring stations in each tract. Canopy and understory species were predominantly native, especially in tracts where ungulates have been excluded.

Hawai'i↗

USGS2017

Influence of restored koa in supporting bird communities

Deforestation of Hawaiian forests has adversely impacted native wildlife, including forest birds, bats and arthropods. Restoration activities have included reforestation with the native koa (Acacia koa), a dominant canopy tree species that is easy to propagate, has high survivorship, and has fast growth rates. We review recent research describing the ecological benefits of koa restoration on wildlife colonization/use, plant dispersal, and native plant recruitment. In general, planting monotypic koa stands can provide forest habitats for species that need them but does not automatically lead to natural regeneration of a diverse forest species assemblage and may require additional restoration activities such as outplanting of other native plants and alien grass control to achieve more natural forest systems. Although early signs of forest and wildlife recovery have been encouraging, the goals of restoration for wildlife conservation versus commercial grade harvesting require different restoration methods.

Hawai'i↗

USGS2017

Hawai`i forest bird monitoring database: Database dictionary

Between 1976 and 1981, the U.S. Fish and Wildlife Service (now U.S. Geological Survey – Pacific Island Ecosystems Research Center [USGS-PIERC]) conducted systematic surveys of forest birds and plant communities on all the main Hawaiian Islands, except O‘ahu, as part of the Hawai‘i Forest Bird Surveys (HFBS). Results of this monumental effort have guided conservation efforts and provided the basis for many plant and bird recovery plans and land acquisition decisions in Hawai‘i. Unfortunately, these estimates and range maps are now seriously outdated, hindering modern conservation decision-making and recovery planning. HFBIDP staff work closely with land managers and others to identify the location of bird populations in need of protection. In addition, HFBIDP is able to assess field collection methods, census areas, and survey frequency for their effectiveness. Survey and geographical data are refined and released in successive versions, each more inclusive, detailed, and accurate than the previous release. Incrementally releasing data gives land managers and survey coordinators reasonably good data to work with early on rather than waiting for the release of ‘perfect’ data, ‘perfectly’ analyzed. Consequently, summary results are available in a timely manner.

Technical Report↗

USGS2017

Monitoring Hawaiian biodiversity: Pilot study to assess changes to forest birds and their habitat

Biological diversity, or biodiversity, is the variety and abundance of species in a defined area, and is one of the oldest and most basic descriptions of biological communities. Understanding how populations and communities are structured and change over space and time in response to internal and external forces is a management priority. Effective management practices and conservation strategies depend on our understanding of the relationship between changes in biodiversity and ecological drivers such as invasive species, land use and climate change. To demonstrate how changes in biodiversity may be monitored over a large (400 km2) tract of native forest habitat, we compared bird and plant community composition and structure in an upper montane region of Hawai‘i Island originally surveyed in 1977 as part of the Hawai‘i Forest Bird Survey (Scott et al. 1986) with a comprehensive sample of the same region in 2015. Our findings suggest that across a region spanning an elevation range of 600 to 2,000 m considerable changes occurred in the plant and bird communities between 1977 and 2015. Endemic and indigenous plants species richness (i.e., total number of species) decreased dramatically in the low and middle elevations below an invasive weed front, whereas naturalized plant species richness did not change between the two periods at any elevation. Endemic bird abundance decreased and two species were lost in the lower elevations (< 1,100 m) between 1977 and 2015, while naturalized bird abundance and the numbers of species increased in the same area. In addition to changes in community composition, the structure of the forest showed evidence of changes in dominant and sub-dominant tree canopy cover, shrub and herbaceous cover, dominant tree canopy height, and matted fern cover. Biodiversity monitoring helps to define specific conservation targets and to measure progress towards reaching those targets. It is difficult to ascribe causative factors to a change in biodiversity without directly manipulating the environment. Forest habitat in a variety of settings (i.e., islands and regions with differing land-use histories and elevation ranges), however, can provide opportunities to evaluate the influence of ecological drivers. Declines in native bird biodiversity in low-elevation areas may be attributed to invasive species as land use and climate conditions have remained relatively similar over the 40-year period. Thus, the shift from an endemic-naturalized co-dominated community in 1977 to one dominated by naturalized, alien birds in 2015, and reduction in native bird abundance over that period, may reflect increasing dominance by naturalized plants within this forested area. Inferences drawn from analyses of region-wide surveys, especially with replicate datasets, will facilitate the identification of broad-scale changes in biodiversity, and provide a needed current datum in Hawaiian plant and bird biodiversity monitoring.

Hawaii↗

USGS2016

Collapsing avian community on a Hawaiian island

The viability of many species has been jeopardized by numerous negative factors over the centuries, but climate change is predicted to accelerate and increase the pressure of many of these threats, leading to extinctions. The Hawaiian honeycreepers, famous for their spectacular adaptive radiation, are predicted to experience negative responses to climate change, given their susceptibility to introduced disease, the strong linkage of disease distribution to climatic conditions, and their current distribution. We document the rapid collapse of the native avifauna on the island of Kaua‘i that corresponds to changes in climate and disease prevalence. Although multiple factors may be pressuring the community, we suggest that a tipping point has been crossed in which temperatures in forest habitats at high elevations have reached a threshold that facilitates the development of avian malaria and its vector throughout these species’ ranges. Continued incursion of invasive weeds and non-native avian competitors may be facilitated by climate change and could also contribute to declines. If current rates of decline continue, we predict multiple extinctions in the coming decades. Kaua‘i represents an early warning for the forest bird communities on the Maui and Hawai‘i islands, as well as other species around the world that are trapped within a climatic space that is rapidly disappearing.

Science Advances↗

USGS2016

State-space modeling of population sizes and trends in Nihoa Finch and Millerbird

Both of the 2 passerines endemic to Nihoa Island, Hawai‘i, USA—the Nihoa Millerbird ( Acrocephalus familiaris kingi ) and Nihoa Finch ( Telespiza ultima )—are listed as endangered by federal and state agencies. Their abundances have been estimated by irregularly implemented fixed-width strip-transect sampling from 1967 to 2012, from which area-based extrapolation of the raw counts produced highly variable abundance estimates for both species. To evaluate an alternative survey method and improve abundance estimates, we conducted variable-distance point-transect sampling between 2010 and 2014. We compared our results to those obtained from strip-transect samples. In addition, we applied state-space models to derive improved estimates of population size and trends from the legacy time series of strip-transect counts. Both species were fairly evenly distributed across Nihoa and occurred in all or nearly all available habitat. Population trends for Nihoa Millerbird were inconclusive because of high within-year variance. Trends for Nihoa Finch were positive, particularly since the early 1990s. Distance-based analysis of point-transect counts produced mean estimates of abundance similar to those from strip-transects but was generally more precise. However, both survey methods produced biologically unrealistic variability between years. State-space modeling of the long-term time series of abundances obtained from strip-transect counts effectively reduced uncertainty in both within- and between-year estimates of population size, and allowed short-term changes in abundance trajectories to be smoothed into a long-term trend.

Hawai'i↗

USGS2016

2015-2016 Palila abundance estimates

The palila (Loxioides bailleui) population was surveyed annually during 1998−2016 on Mauna Kea Volcano to determine abundance, population trend, and spatial distribution. In the latest surveys, the 2015 population was estimated at 852−1,406 birds (point estimate: 1,116) and the 2016 population was estimated at 1,494−2,385 (point estimate: 1,934). Similar numbers of palila were detected during the first and subsequent counts within each year during 2012−2016; the proportion of the total annual detections in each count ranged from 46% to 56%; and there was no difference in the detection probability due to count sequence. Furthermore, conducting repeat counts improved the abundance estimates by reducing the width of the confidence intervals between 9% and 32% annually. This suggests that multiple counts do not affect bird or observer behavior and can be continued in the future to improve the precision of abundance estimates. Five palila were detected on supplemental survey stations in the Ka‘ohe restoration area, outside the core survey area but still within Palila Critical Habitat (one in 2015 and four in 2016), suggesting that palila are present in habitat that is recovering from cattle grazing on the southwest slope. The average rate of decline during 1998−2016 was 150 birds per year. Over the 18-year monitoring period, the estimated rate of change equated to a 58% decline in the population.

Technical Report↗

USGS2015

Comparative demographics of a Hawaiian forest bird community

Estimates of demographic parameters such as survival and reproductive success are critical for guiding management efforts focused on species of conservation concern. Unfortunately, reliable demographic parameters are difficult to obtain for any species, but especially for rare or endangered species. Here we derived estimates of adult survival and recruitment in a community of Hawaiian forest birds, including eight native species (of which three are endangered) and two introduced species at Hakalau Forest National Wildlife Refuge, Hawaiʻi. Integrated population models (IPM) were used to link mark–recapture data (1994–1999) with long-term population surveys (1987–2008). To our knowledge, this is the first time that IPM have been used to characterize demographic parameters of a whole avian community, and provides important insights into the life history strategies of the community. The demographic data were used to test two hypotheses: 1) arthropod specialists, such as the ‘Akiapōlā‘au Hemignathus munroi , are ‘slower’ species characterized by a greater relative contribution of adult survival to population growth, i.e. lower fecundity and increased adult survival; and 2) a species’ susceptibility to environmental change, as reflected by its conservation status, can be predicted by its life history traits. We found that all species were characterized by a similar population growth rate around one, independently of conservation status, origin (native vs non-native), feeding guild, or life history strategy (as measured by ‘slowness’), which suggested that the community had reached an equilibrium. However, such stable dynamics were achieved differently across feeding guilds, as demonstrated by a significant increase of adult survival and a significant decrease of recruitment along a gradient of increased insectivory, in support of hypothesis 1. Supporting our second hypothesis, we found that slower species were more vulnerable species at the global scale than faster ones. The possible causes and conservation implications of these patterns are discussed.

Hawaii↗

USGS2015

Evaluating abundance and trends in a Hawaiian avian community using state-space analysis

Estimating population abundances and patterns of change over time are important in both ecology and conservation. Trend assessment typically entails fitting a regression to a time series of abundances to estimate population trajectory. However, changes in abundance estimates from year-to-year across time are due to both true variation in population size (process variation) and variation due to imperfect sampling and model fit. State-space models are a relatively new method that can be used to partition the error components and quantify trends based only on process variation. We compare a state-space modelling approach with a more traditional linear regression approach to assess trends in uncorrected raw counts and detection-corrected abundance estimates of forest birds at Hakalau Forest National Wildlife Refuge, Hawai‘i. Most species demonstrated similar trends using either method. In general, evidence for trends using state-space models was less strong than for linear regression, as measured by estimates of precision. However, while the state-space models may sacrifice precision, the expectation is that these estimates provide a better representation of the real world biological processes of interest because they are partitioning process variation (environmental and demographic variation) and observation variation (sampling and model variation). The state-space approach also provides annual estimates of abundance which can be used by managers to set conservation strategies, and can be linked to factors that vary by year, such as climate, to better understand processes that drive population trends.

Hawai'i↗

USGS2015

Current land bird distribution and trends in population abundance between 1982 and 2012 on Rota, Mariana Islands

The western Pacific island of Rota is the fourth largest human-inhabited island in the Mariana archipelago and designated an Endemic Bird Area. Between 1982 and 2012, 12 point-transect distance-sampling surveys were conducted to assess bird population status. Surveys did not consistently sample the entire island; thus, we used a ratio estimator to estimate bird abundances in strata not sampled during every survey. Trends in population size were reliably estimated for 11 of 13 bird species, and 7 species declined over the 30-y time series, including the island collared-dove Streptopelia bitorquata , white-throated ground-dove Gallicolumba xanthonura , Mariana fruit-dove Ptilinopus roseicapilla , collared kingfisher Todiramphus chloris orii , Micronesian myzomela Myzomela rubratra , black drongo Dicrurus macrocercus , and Mariana crow Corvus kubaryi . The endangered Mariana crow (x̄ = 81 birds, 95% CI 30–202) declined sharply to fewer than 200 individuals in 2012, down from 1,491 birds in 1982 (95% CI = 815–3,115). Trends increased for white tern Gygis alba , rufous fantail Rhipidura rufifrons mariae , and Micronesian starling Aplonis opaca . Numbers of the endangered Rota white-eye Zosterops rotensis declined from 1982 to the late 1990s but returned to 1980s levels by 2012, resulting in an overall stable trend. Trends for the yellow bittern Ixobrychus sinensis were inconclusive. Eurasian tree sparrow Passer montanus trends were not assessed; however, their numbers in 1982 and 2012 were similar. Occupancy models of the 2012 survey data revealed general patterns of land cover use and detectability among 12 species that could be reliably modeled. Occupancy was not assessed for the Eurasian tree sparrow because of insufficient detections. Based on the 2012 survey, bird distribution and abundance across Rota revealed three general patterns: 1) range restriction, including Mariana crow, Rota white-eye, and Eurasian tree sparrow; 2) widespread distribution, low abundance, including collared kingfisher, island collared-dove, white-throated ground-dove, Mariana fruit-dove, white tern, yellow bittern, black drongo, and Micronesian myzomela; and 3) widespread distribution, high abundance, including rufous fantail and Micronesian starling. The Mariana crow was dispersed around the periphery of the island in steep forested land-cover types. In contrast, the Rota white-eye was restricted to the high-elevation mesa. Only for the white-throated ground-dove was there a significant difference among cover types, with lower occupancy in open field than in forested areas. Vegetation was included in the best-fit occupancy models for yellow bittern, black drongo, Micronesian myzomela, and Micronesian starling, but vegetation type was not a significant variable nor included in the top models for the remaining five species: white tern, island collared-dove, Mariana fruit-dove, collared kingfisher, and rufous fantail. Given declining population trends, the Rota bird-monitoring program could benefit from establishing threshold and alert limits and identifying alternative research and management actions. Continued monitoring and demographic sampling, in conjunction with ecological studies, are needed to understand why most bird species on Rota are declining, identify the causative agents, and assess effectiveness of conservation actions, especially for the Mariana crow.

Rota↗

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.

Hawaii↗

USGS2014

Terrestrial bird population trends on Aguiguan (Goat Island), Mariana Islands

The island of Aguiguan is part of the Mariana archipelago and currently supports populations of four endemic species, including one endemic genus, Cleptornis . Bird population trends since 1982 were recently assessed on the neighbouring islands of Saipan, Tinian, and Rota indicating declines in some native species. Point-transect surveys were conducted in 2008 by the U.S. Fish and Wildlife Service to assess population densities and trends on Aguiguan. Densities for six of the nine native birds—White-throated Ground-dove Gallicolumba xanthonura , Collared Kingfisher Todiramphus chloris , Rufous Fantail Rhipidura rufifrons , Golden White-eye Cleptornis marchei , Bridled White-eye Zosterops conspicillatus and Micronesian Starling Aplonis opaca —and the non-native bird—Island Collared-dove Streptopelia bitorquata —were significantly greater in 2008 than in 1982. No differences in densities were detected among the surveys for Mariana Fruit-dove Ptilinopus roseicapilla , and Micronesian Myzomela Myzomela rubratra . Three federally and locally listed endangered birds—Nightingale Reed-warbler Acrocephalus luscinius , Mariana Swiftlet Collocalia bartschi , and Micronesian Megapode Megapodius laperous )—were either not detected during the point-transect counts, the surveys were not appropriate for the species, or the numbers of birds detected were too small to estimate densities. The factors behind the increasing trends for some species are unknown but may be related to increased forest cover on the island since 1982. With declining trends for some native species on neighbouring islands, the increasing and stable trends on Aguiguan is good news for forest bird populations in the region, as Aguiguan populations can help support conservation efforts on other islands in the archipelago.

Aguiguan Island, Mariana Islands↗

USGS2014

Changing climate and the altitudinal range of avian malaria in the Hawaiian Islands: an ongoing conservation crisis on the island of Kaua'i

Transmission of avian malaria in the Hawaiian Islands varies across altitudinal gradients and is greatest at elevations below 1500 m where both temperature and moisture are favorable for the sole mosquito vector, Culex quinquefasciatus, and extrinsic sporogonic development of the parasite, Plasmodium relictum. Potential consequences of global warming on this system have been recognized for over a decade with concerns that increases in mean temperatures could lead to expansion of malaria into habitats where cool temperatures currently limit transmission to highly susceptible endemic forest birds. Recent declines in two endangered species on the island of Kaua'i, the ‘Akikiki (Oreomystis bairdi) and ‘Akeke'e (Loxops caeruleirostris), and retreat of more common native honeycreepers to the last remaining high elevation habitat on the Alaka'i Plateau suggest that predicted changes in disease transmission may be occurring. We compared prevalence of malarial infections in forest birds that were sampled at three locations on the Plateau during 1994–1997 and again during 2007–2013, and also evaluated changes in the occurrence of mosquito larvae in available aquatic habitats during the same time periods. Prevalence of infection increased significantly at the lower (1100 m, 10.3% to 28.2%), middle (1250 m, 8.4% to 12.2%), and upper ends of the Plateau (1350 m, 2.0% to 19.3%). A concurrent increase in detections of Culex larvae in aquatic habitats associated with stream margins indicates that populations of the vector are also increasing. These increases are at least in part due to local transmission because overall prevalence in Kaua'i ‘Elepaio (Chasiempis sclateri), a sedentary native species, has increased from 17.2% to 27.0%. Increasing mean air temperatures, declining precipitation, and changes in streamflow that have taken place over the past 20 years are creating environmental conditions throughout major portions of the Alaka'i Plateau that support increased transmission of avian malaria.

Hawai'i↗

USGS2014

Hawaiian forest bird trends: using log-linear models to assess long-term trends is supported by model diagnostics and assumptions (reply to Freed and Cann 2013)

Freed and Cann (2013) criticized our use of linear models to assess trends in the status of Hawaiian forest birds through time (Camp et al. 2009a, 2009b, 2010) by questioning our sampling scheme, whether we met model assumptions, and whether we ignored short-term changes in the population time series. In the present paper, we address these concerns and reiterate that our results do not support the position of Freed and Cann (2013) that the forest birds in the Hakalau Forest National Wildlife Refuge (NWR) are declining, or that the federally listed endangered birds are showing signs of imminent collapse. On the contrary, our data indicate that the 21-year long-term trends for native birds in Hakalau Forest NWR are stable to increasing, especially in areas that have received active management.

Hawai'i↗

USGS2014

Status of forest birds on Rota, Mariana Islands

The western Pacific island of Rota is the third largest human inhabited island in the Mariana archipelago, and is designated an Endemic Bird Area. Between 1982 and 2012, 12 point-transect distance sampling surveys were conducted to assess population status. Surveys did not consistently sample the entire island; thus, we used a ratio estimator to estimate bird abundances in strata not sampled during every survey. Occupancy models of the 2012 survey revealed general patterns of habitat use and detectability among 11 species that could be reliably modeled. The endangered Mariana crow ( Corvus kubaryi ) was dispersed around the periphery of the island in steep forested habitats. In contrast, the endangered Rota white-eye ( Zosterops rotensis ) was restricted to the high-elevation mesa. Precision of detection probabilities and occupancy estimates and effects of habitat types, sampling conditions, and specific observers varied considerably among species, indicating that more narrowly defined classifications and additional observer training may improve the accuracy of predictive modeling. Population estimates of five out of ten native bird species, including collared kingfisher ( Todiramphus chloris orii ), Mariana crow, Mariana fruit-dove ( Ptilinopus roseicapilla ), Micronesian myzomela ( Myzomela rubrata ), and white-throated ground-dove ( Gallicolumba xanthonura ) declined over the 30-year time series. The crow declined sharply to fewer than 200 individuals (upper 95% confidence interval). Trends increased for Micronesian starling ( Aplonis opaca ), rufous fantail ( Rhipidura rufifrons mariae ), and white tern ( Gygis alba ). Rota white-eye numbers declined from 1982 to the late 1990s, but returned to 1980s levels by 2012. The trend for the yellow bittern ( Ixobrychus sinensis ) was inconclusive. The alien Eurasian tree sparrow ( Passer montanus ) apparently increased in number despite an unreliable trend assessment. Declines were noted in the other two alien birds, black drongo ( Dicrurus macrocercus ) and island collared-dove ( Streptopelia bitorquata ). Total bird densities on Rota were similar to those on Saipan and Tinian, which were lower than densities on Aguiguan. Overall, bird trends on Rota declined, whereas trends observed for the same period on Saipan and Tinian were mixed, and trends on Aguiguan were stable to increasing. We identified several sampling design and protocol procedures that may improve the precision of occupancy, status, and trend assessments. Continued monitoring and demographic sampling are needed to understand why most bird species on Rota are declining, to identify the causative agents, and to assess effectiveness of conservation actions for rare species, especially the Mariana crow.

Marianas Islands↗

USGS2014

Monitoring Hawaiian waterbirds: evaluation of sampling methods to produce reliable estimates

We conducted field trials to assess several different methods of estimating the abundance of four endangered Hawaiian waterbirds: the Hawaiian duck ( Anas wyvilliana ), Hawaiian coot ( Fulica alai ), Hawaiian common moorhen ( Gallinula chloropus sandvicensis ) and Hawaiian stilt ( Himantopus mexicanus knudseni ). At two sites on Oʽahu, James Campbell National Wildlife Refuge and Hamakua Marsh, we conducted field trials where both solitary and paired observers counted birds and recorded the distance to observed birds. We then compared the results of estimates using the existing simple count, distance estimates from both point- and line-transect surveys, paired observer count estimates, bounded count, and Overton estimators. Comparing covariate recorded values among simultaneous observations revealed inconsistency between observers. We showed that the variation among simple counts means the current direct count survey, even if interpreted as a proportional index of abundance, incorporates many sources of uncertainty that are not taken into account. Analysis revealed violation of model assumptions that allowed us to discount distance-based estimates as a viable estimation technique. Among the remaining methods, point counts by paired observers produced the most precise estimates while meeting model assumptions. We present an example sampling protocol using paired observer counts. Finally, we suggest further research that will improve abundance estimates of Hawaiian waterbirds.

Hawai'i↗

USGS2013

Response of palila and other subalpine Hawaiian forest bird species to prolonged drought and habitat degradation by feral ungulates

Extinction has claimed half of all historically-known Hawaiian passerines, and today many extant species are increasingly threatened due to the combined effects of invasive species and climate change. Habitat disturbance has affected populations of feeding specialists most profoundly, and our results indicate that specialists continue to be most vulnerable, although even some abundant, introduced, generalist species also may be affected. Surveys of passerines during 1998–2011 in subalpine woodland habitat on Mauna Kea Volcano, Island of Hawai′i, revealed that the abundance of the critically endangered palila ( Loxioides bailleui ), a seed specialist, declined by 79% after 2003. The ′akiapōlā′au ( Hemignathus munroi ), an endangered specialist insectivore, was not detected in the survey area after 1998. The Hawai′i ′amakihi ( Hemignathus virens virens ), a generalist feeder and the most abundant species on Mauna Kea, was the only native species to maintain a stable population. The Japanese white-eye ( Zosterops japonicus ), a well-entrenched generalist and one of the three most common introduced species, declined. Drought prevailed in 74% of months during 2000–2011, and dry conditions contributed to the recent decline of the palila by reducing the annual māmane ( Sophora chrysophylla ) seed pod crop, which influences palila breeding and survival. Sustained browsing by introduced ungulates also lowered habitat carrying capacity, and their elimination should reduce the effects of drought and promote forest restoration. Our results illustrate how the feeding ecology of a species can influence its response to interacting environmental perturbations, and they underscore the value of long-term monitoring to detect population trends of sensitive species.

Hawai'i↗

USGS2013

Abundance, distribution, and population trends of the iconic Hawaiian Honeycreeper, the ʻIʻiwi (Vestiaria coccinea) throughout the Hawaiian Islands

Naturalists in the 1800s described the ʻIʻiwi (Vestiaria coccinea) as one of the most abundant forest birds, detected in forested areas from sea level to tree line across all the major Hawaiian Islands. However, in the late 1800s, ʻIʻiwi began to disappear from low elevation forests, and by the mid-1900s, the species was largely absent from low- and mid-elevation areas. Today, ʻIʻiwi are restricted to high-elevation forests on the islands of Hawaiʻi, east Maui, and Kauaʻi, with a few birds apparently persisting on Oʻahu, Molokaʻi, and west Maui. ʻIʻiwi are highly vulnerable to introduced disease, and the prevalence of avian malaria in low and mid-elevations is believed to be the cause of ʻIʻiwi being restricted to high elevations where temperatures are too cold for the development of the disease and its mosquito vector. With global warming, it is feared that the disease will move quickly into the high-elevation forests where the last ʻIʻiwi reside, threatening their viability. The U.S. Fish and Wildlife Service was petitioned to list the ʻIʻiwi as an Endangered Species in 2010, and this report provides a comprehensive review of the abundance, distribution, and trends using historical survey data as well as the most recently available survey information (up to 2012). We estimate the total population size of ‘I‘iwi at 550,972–659,864 (mean = 605,418) individuals. Of these, 90 percent are on the island of Hawaiʻi, followed by east Maui (about 10 percent), with less than 1 percent on Kauaʻi. ʻIʻiwi population trends vary across the islands. ʻIʻiwi population in Kauaʻi has experienced sharp declines, with a projected trend of 92 percent decline over a 25 year period based on the 2000–2012 surveys. On East Maui, the northeastern region has experienced declines (34 percent over a 25 year period), while the southeastern region has been stable to moderately increasing. On the island of Hawaiʻi, population trends are mixed. On the windward side, populations are largely declining, although the northern section (Hakalau Forest) has stable populations. On the leeward side, results suggest a strongly increasing population, with estimates of as much as a 147 percent increase over a 25 year period from the Puʻu Waʻawaʻa region. However, it is unclear how much these results from the leeward side of Hawaiʻi show a population trend contrary to population trends in all other areas or are an artifact of a sparsely sampled area. Trends by elevation suggest a large decrease in numbers of ʻIʻiwi at elevations below 1,200 meters on Kauaʻi and northeast Maui. Low elevation ʻIʻiwi populations also appear to have decreased in other regions, although low-elevation areas are not surveyed as often as other areas because of their lack of native forest birds. An exception to this pattern was the lower portions of the Hakalau Forest National Wildlife Refuge Kona Unit in the central leeward part of the island of Hawaiʻi, where populations appeared stable at the lower elevations. Based on the most recent surveys (up to 2012), approximately 50 percent of ʻIʻiwi live in a narrow, 500-meter band at elevations of 1,200–1,700 meters, suggesting that ʻIʻiwi are vulnerable to future shifts in climate.

Hawai'i↗