UH System Repository :: Browsing by Author "Gorressen, P. Marcos"

Browsing by Author "Gorressen, P. Marcos"

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2011 Kiwikiu (Maui Parrotbill) and Maui `alauahio abundance estimates and the effect of sampling effort on power to detect a trend.
(2016-01-25) Brinck, Kevin; Camp, Richard; Gorressen, P. Marcos; Leonard, David; Mounce, Hanna; Iknayan, Kelly; Paxton, Eben
The Kiwikiu (Pseudonestor xanthophrys), also called the Maui Parrotbill, is an endangered, forest bird found only in high elevation, wet forest of the eastern portion of Maui Island. Recent surveys, conducted at five year intervals, have revealed wide variation in abundance estimates (Camp et al. 2009). Effective management and conservation requires accurate estimates of abundance, which is difficult for rare species such as the Kiwikiu because low density leads to few observations, resulting in low sample size and high uncertainty in abundance estimates. In addition to being rare, they occur in remote, difficult to access terrain, which makes them difficult to detect and further reduces the accuracy of counts. The Maui `Alauahio (Paroreomyza montana), sometimes called the Maui Creeper, historically occupied the entire island of Maui (Gorresen et al. 2009). It has since been extirpated from much of its original habitat and now occurs in forested areas of East Maui where its habitat overlaps with that of the Kiwikiu. Though they share the same habitat, the `Alauahio is much more abundant—by more than two orders of magnitude—and occurs over a wider range than the Kiwikiu. Both species appear to have no statistically significant population trend from 1980–2001, but abundance estimates vary widely from survey to survey and have wide uncertainties (Camp et al. 2009). Ideally survey design should result in estimates precise enough to be able to detect significant declines in abundance that may trigger management intervention. We wished to improve the accuracy of Kiwikiu abundance estimates and the ability to detect significant trends in abundance. To that end, in 2011, repeated point count surveys were conducted across the Kiwikiu range, excluding Haleakalā National Park (Figure 1). The increased sampling effort increases sample size and improves the precision of estimates, and repeat samples also allowed us to partition within-year and between-year variation in surveys, increasing the statistical power to detect trends.
A five-year study of Hawaiian hoary bat (Lasiurus cinereus semotus) occupancy on the island of Hawai`i
(2016-01-25) Gorressen, P. Marcos; Bonaccorso, Frank; Pinzari, Corinna; Todd, Christopher; Montoya-Aiona, Kristina; Brinck, Kevin
Using acoustic recordings of the vocalizations of the endangered Hawaiian hoary bat (Lasiurus cinereus semotus) collected over a five-year period (2007–2011) from 25 survey areas across the island of Hawai`i, we modeled the relationship between habitat attributes and bat occurrence. Our data support the conclusion that hoary bats concentrate in the coastal lowlands of Hawai`i during the breeding season, May through October, and migrate to interior highlands during the winter non-breeding season. Highest occupancy peaked on the Julian date 15 September across the five-year average and during the season of fledging by the young of the year. Although the Hawaiian hoary bat is a habitat generalist species and occurs from sea level to the highest volcanic peaks on Hawai`i, there was a significant association between occupancy and the prevalence of mature forest cover. Trends in occupancy were stable to slightly increasing during the breeding season over the five years of our surveys.
Avian monitoring entry form version 2.1 Hawai`i forest bird inter-agency database project
(2016-01-25) Camp, Richard; Lam, Roger; Matsui, Victoriya; Cramer, Ashley; Pratt, Thane; Woodsworth, Bethany; Gorressen, P. Marcos; Nash, Sarah
From 1976–1981, the U.S. Fish and Wildlife Service conducted systematic surveys of forest birds and plant communities on the main Hawaiian Islands as part of the Hawaii Forest Bird Surveys (HFBS; Scott et al. 1986) Since the HFBS, more than 600 surveys of forest birds have been conducted in Hawai`i a variety of organizations, including the National Park Service, U.S. Fish and Wildlife Service, U.S. Forest Service, Hawai`i Department of Land and Natural Resources, Kamehameha Schools, University of Hawai`i, The Nature Conservancy, and private consultants. Prior to the initiation of the present project, these surveys were scattered among many different individuals and agencies, and most had never been entered into a computer, analyzed, or reported. These survey data represent a phenomenal informational resource that has not previously been widely available. The Hawai`i Forest Bird Interagency Database Project (HFBIDP) has as its goals to make these data usable and accessible by creating a centralized, standardized database of all forest bird surveys collected since the HFBS; develop current population size estimates, species-habitat models, and distribution maps for all native and exotic forest birds in Hawai`i; examine population trends in species of concern; and present these results in publications and on a webpage, making them available to cooperators throughout Hawai`i.
Behavior of the Hawaiian hoary bat (Lasiurus cinereus semotus) at wind turbines and its distribution across the North Ko`olau mountains, O'ahu
(2015-05) Gorressen, P. Marcos; Cryan, Paul; Huso, Manuela; Hein, Cris; Schirmacher, Michael; Johnson, Jessica; Montoya-Aiona, Kristina; Brinck, Kevin; Bonaccorso, Frank
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.
Developing accurate survey methods for estimating population sizes and trends of the critically endangered Nihoa millerbird and Nihoa finch.
(2016-01-25) Gorressen, P. Marcos; Camp, Richard; Brinck, Kevin; Farmer, Chris
This report describes the results of a comparative study of bird survey methods undertaken for the purpose of improving assessments of the conservation status for the two endemic passerines on the Island of Nihoa—Nihoa Millerbird (Sylviidae: Acrocephalus familiaris kingi) and Nihoa Finch (Fringilidae: Telespiza ultima; also referred herein as millerbird and finch)—both listed as endangered under the Federal Endangered Species Act (ESA) and Hawai`i Revised Statutes 195D. The current survey protocol, implemented since 1967, has produced a highly variable range of counts for both the millerbird and finch, making difficult assessments of population size and trend. This report details the analyses of bird survey data collected in 2010 and 2011 in which three survey methods were compared―strip-transect, line-transect, and point-transect sampling―and provides recommendations for improved survey methods and protocols. Funding for this research was provided through a Science Support Partnership grant sponsored jointly by the U.S. Geological Survey (USGS) and the U.S. Fish and Wildlife Service (USFWS). Point-transect surveys indicated that millerbirds were more abundant than shown by the strip-transect method, and were estimated at 802 birds in 2010 (95%CI = 652 – 964) and 704 birds in 2011 (95%CI = 579 – 837). Point-transect surveys yielded population estimates with improved precision which will permit trends to be detected in shorter time periods and with greater statistical power than is available from strip-transect survey methods. Mean finch population estimates and associated uncertainty were not markedly different among the three survey methods, but the performance of models used to estimate density and population size are expected to improve as the data from additional surveys are incorporated. Using the point-transect survey, the mean finch population size was estimated at 2,917 birds in 2010 (95%CI = 2,037 – 3,965) and 2,461 birds in 2011 (95%CI = 1,682 – 3,348). Preliminary testing of the line-transect method in 2011 showed that it would not generate sufficient detections to effectively model bird density, and consequently, relatively precise population size estimates. Both species were fairly evenly distributed across Nihoa and appear to occur in all or nearly all available habitat. The time expended and area traversed by observers was similar among survey methods; however, point-transect surveys do not require that observers walk a straight transect line, thereby allowing them to avoid culturally or biologically sensitive areas and minimize the adverse effects of recurrent travel to any particular area. In general, point-transect surveys detect more birds than strip-survey methods, thereby improving precision and resulting population size and trend estimation. The method is also better suited for the steep and uneven terrain of Nihoa.
Developing accurate survey methods for estimating population sizes and trends of the critically endangered Nihoa millerbird and Nihoa finch.
(2012-10) Gorressen, P. Marcos; Camp, Richard; Brinck, Kevin; Farmer, Chris
This report describes the results of a comparative study of bird survey methods undertaken for the purpose of improving assessments of the conservation status for the two endemic passerines on the Island of Nihoa—Nihoa Millerbird (Sylviidae: Acrocephalus familiaris kingi) and Nihoa Finch (Fringilidae: Telespiza ultima; also referred herein as millerbird and finch)—both listed as endangered under the Federal Endangered Species Act (ESA) and Hawai`i Revised Statutes 195D. The current survey protocol, implemented since 1967, has produced a highly variable range of counts for both the millerbird and finch, making difficult assessments of population size and trend. This report details the analyses of bird survey data collected in 2010 and 2011 in which three survey methods were compared―strip-transect, line-transect, and point-transect sampling―and provides recommendations for improved survey methods and protocols. Funding for this research was provided through a Science Support Partnership grant sponsored jointly by the U.S. Geological Survey (USGS) and the U.S. Fish and Wildlife Service (USFWS). Point-transect surveys indicated that millerbirds were more abundant than shown by the strip-transect method, and were estimated at 802 birds in 2010 (95%CI = 652 – 964) and 704 birds in 2011 (95%CI = 579 – 837). Point-transect surveys yielded population estimates with improved precision which will permit trends to be detected in shorter time periods and with greater statistical power than is available from strip-transect survey methods. Mean finch population estimates and associated uncertainty were not markedly different among the three survey methods, but the performance of models used to estimate density and population size are expected to improve as the data from additional surveys are incorporated. Using the point-transect survey, the mean finch population size was estimated at 2,917 birds in 2010 (95%CI = 2,037 – 3,965) and 2,461 birds in 2011 (95%CI = 1,682 – 3,348). Preliminary testing of the line-transect method in 2011 showed that it would not generate sufficient detections to effectively model bird density, and consequently, relatively precise population size estimates. Both species were fairly evenly distributed across Nihoa and appear to occur in all or nearly all available habitat. The time expended and area traversed by observers was similar among survey methods; however, point-transect surveys do not require that observers walk a straight transect line, thereby allowing them to avoid culturally or biologically sensitive areas and minimize the adverse effects of recurrent travel to any particular area. In general, point-transect surveys detect more birds than strip-survey methods, thereby improving precision and resulting population size and trend estimation. The method is also better suited for the steep and uneven terrain of Nihoa.
Forest bird monitoring protocol for strategic habitat conservation and endangered species management on O`ahu Forest National Wildlife Refuge, Island of O`ahu, Hawai`i.
(2016-01-26) Camp, Richard; Gorressen, P. Marcos; Banko, Paul
This report describes the results of a pilot forest bird survey and a consequent forest bird monitoring protocol that was developed for the O‘ahu Forest National Wildlife Refuge, O‘ahu Island, Hawai‘i. The pilot survey was conducted to inform aspects of the monitoring protocol and to provide a baseline with which to compare future surveys on the Refuge. The protocol was developed in an adaptive management framework to track bird distribution and abundance and to meet the strategic habitat conservation requirements of the Refuge. Funding for this research was provided through a Science Support Partnership grant sponsored jointly by the U.S. Geological Survey (USGS) and the U.S. Fish and Wildlife Service (USFWS). Between 28 February and 17 May, 2011, we established and carried out pilot point-transect surveys at 33 stations within the Refuge. In general, the sampling conditions were good during the surveys. We detected only two native forest birds, O‘ahu ‘Amakihi (Hemignathus flavus) and ‘Apapane (Himatione sanguinea), during surveys, and we did not detect O‘ahu ‘Elepaio (Chasiempis ibidus) or ‘I‘iwi (Vestiaria coccinea) at any time on the Refuge. Abundances of both native species were too low to estimate population densities on the Refuge, but a larger scale survey would likely yield sufficient numbers of O‘ahu ‘Amakihi to estimate their density. We also detected nine alien forest bird species, four of which were observed in sufficient numbers to estimate densities. Results from the pilot study were used to inform a monitoring protocol designed to track forest bird distribution and abundance on the Refuge. Questions most relevant to management that are addressed by the protocol are: 1) are the distributions of forest bird species changing; and 2) are population abundances changing? Of the two parameters being measured, distribution can be ascertained from point-transect sampling methods for all native and alien passerine forest birds. On the other hand, the very low abundance of native birds evident during our survey presents a formidable challenge to monitoring population trends over short (annual) to moderate (5-50 year) time scales. To maximize the detection of native birds, we recommend that surveys be conducted during the period of peak bird vocalization, generally from late February to early April. Nevertheless, as a practical matter, it seems unlikely that even greatly increased survey effort will be sufficient to overcome the problem of low detection rates for most native species; thus, we did not develop alert limits that might otherwise be used to trigger actions to arrest population declines. Instead, identifying major factors limiting bird populations and developing methods of reducing threats would seem potentially more useful in guiding management. The pilot study data serves as a core set of routes/stations for future surveys; however, the sampling effort will need to be expanded geographically to increase detections of uncommon species and to cover a larger, more representative area of the Refuge. The uncertainty in densities ranged from low to very large; thus, detecting trends will be difficult. Increasing the numbers of stations sampled is expected to reduce uncertainty and yield greater power to detect trends. A modest sampling effort, about 90 stations, is likely to produce low to moderate levels of uncertainty for most species, which should allow for detecting large trends (>50% change) in density over long sampling durations (e.g., >50 years). Sampling at this level should provide sufficient detections to quantitatively monitor O‘ahu ‘Amakihi, as well as four non-native birds—Red-vented Bulbul (Pycnonotus cafer), Japanese Bush-Warbler (Cittia diphone), Redbilled Leiothrix (Leiothrix lutea) and Japanese White-eye (Zosterops japonicus). This level of sampling will also provide coverage across the refuge, instead of concentrating the effort in only one portion. In addition to surveying for many decades, conducting the surveys frequently, either annually or biennially, will increase the power necessary to detect trends. This monitoring protocol can be implemented incrementally while addressing management and conservation needs. This protocol will be most effective, however, when implemented with management actions and research needed to identify the main factors responsible for low population abundances of native species.
Rare and endangered species of Hawai`i Volcanoes National Park
(2016-01-26) Pratt, Linda; Pratt, Thane; Foote, David; Gorressen, P. Marcos
Hawai`i Volcanoes National Park (HAVO) is the largest area in the State of Hawai`i protected for its geology and landscapes and its native flora and fauna. The park covers approximately 135,000 hectares or 333,000 acres in all. These lands stretch from the seacoast of Kīlauea Volcano to far above timberline on the summit of Mauna Loa (Figure 1). This vast area includes expanses of forests, woodlands, shrublands, and barren lava flows that represent an array of native ecosystems. Contained within these communities are a great many species of rare animals and plants, most of them unique to the island of Hawai`i, and some of them surviving only in the park. These are the biological treasures of Hawai`i Volcanoes National Park. Our book is a guide to all animal and plant species in HAVO that are specially recognized as endangered species in the general sense. (The official designations at four levels and the unofficial designation of species of concern are explained later.) There are 23 such animal species and 71 plant species covered in the handbook, including six species planted in HAVO but not naturally occurring. In addition, we describe seven rare communities. In some cases, HAVO offers the best opportunity to save these species and communities from extinction. Increasingly, the park has attempted to restore rare populations by conducting surveys to locate them, controlling threats such as feral livestock, and bolstering existing populations or creating new ones by planting nursery stock. To aid such efforts, our original intent was to publish an identification guide for researchers and field management personnel. Particularly, we wanted to familiarize the reader with the many rare plant species which otherwise are known mainly from the technical literature. Because we soon came to realize that this handbook would be useful to a much larger, general readership, our aim is to make this information available to anyone interested in endangered animals and plants at Hawai`i Volcanoes National Park.
Status of forest birds on Rota, Mariana Islands.
(2016-01-25) Camp, Richard; Brinck, Kevin; Gorressen, P. Marcos; Amidon, Fred; Radley, Paul; Berkowitz, S. Paul; Banko, Paul
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.

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