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Browsing by Author "Camp, Richard"

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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.
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.
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.
Monitoring Hawaiian waterbirds: evaluation of sampling methods to produce reliable estimates.
(2016-01-25) Camp, Richard; Brinck, Kevin; Paxton, Kevin; Leopold, Christina
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.
Nihoa and Laysan Island passerines population abundances, trends, and habitat utilization
(2024-06-18) Bak, Trevor; Camp, Richard; Farmer, Chris; Rounds, Rachel; Plentovich, Sheldon; Vetter, John; Banko, Paul; Nash, Sarah
Nihoa and Laysan Island, part of the Northwestern Hawaiian Islands, are host to three endangered passerine species—Nihoa finch (Telespiza ultima), Nihoa millerbird (Acrocephalus familiaris kingi), and Laysan finch (Telespiza cantans). Using point-transect distance sampling survey records from 2010 to 2022 for Nihoa and 2013 to 2019 for Laysan Island, we estimated the density and abundance of all three species. We also compared densities between habitats for both islands, classifying Nihoa habitat as Eragrostis (grass) or mixed shrub and Laysan Island as open or dense habitat. The population of Nihoa finch remained stable with slight fluctuations among years, with a population size of 6,592 (4,954–8,655) birds for the most recent sampling year, 2022. Laysan finch also remained stable with a total population in both dense and open habitat of 17,657 (11,994–23,320) for the most recent sampling year, 2019. The Nihoa millerbird significantly increased on both Nihoa and Laysan Island with a global population of 1,907 (1,291–2,766) in 2019, the most recent year both islands were sampled. Overall, the populations of these three endangered species were stable or increasing. The increase of Nihoa millerbird on Laysan Island, after being translocated to the island in 2011 and 2012, represents the successful establishment of a second viable population, leading to a decrease in the species’ IUCN extinction risk status (from critically endangered to endangered). Continued population monitoring of these endangered species can help inform future management actions and ensure their preservation into the future.
Palila abundance and trend
(2016-01-25) Camp, Richard; Banko, Paul
The Palila (Loxioides bailleui) is an endangered, seed-eating, finch-billed honeycreeper found only on Hawai`i Island. Once occurring on the islands of Kaua`i and O`ahu and Mauna Loa and Hualālai volcanoes of Hawai`i, Palila are now found only in subalpine, dry-forest habitats on Mauna Kea (Banko et al. 2002). Previous analyses showed that Palila numbers fluctuated throughout the 1980s and 1990s but declined rapidly and steadily since 2003 (Jacobi et al. 1996, Leonard et al. 2008, Banko et al. 2009, Gorresen et al. 2009, Banko et al. in press). The aim of this report is to update abundance estimates for the Palila based on the 2012 surveys. We assess Palila trends over two periods: 1) the long-term trend during 1998–2012 and 2) the short-term trajectory between 2003 and 2012. The first period evaluates the population trend for the entire time series since additional transects were established (Johnson et al. 2006). These additional transects were established to produce a more precise population estimate and provide more complete coverage of the Palila range. The initial year for short-term trajectory was chosen subjectively to coincide with the recent decline in the Palila population. Additionally, stations in the core Palila habitat were surveyed on two occasions in 2012, thus allowing us to address the question of how repeat samples improve estimate precision.
Palila abundance estimates and trend
(2016-01-24) Camp, Richard; Brink, Kevin; Banko, Paul
The palila (Loxioides bailleui) population was surveyed annually during 1998−2014 on Mauna Kea Volcano to determine abundance, population trend, and spatial distribution. In the latest surveys, the 2013 population was estimated at 1,492−2,132 birds (point estimate: 1,799) and the 2014 population was estimated at 1,697−2,508 (point estimate: 2,070). Similar numbers of palila were detected during the first and subsequent counts within each year during 2012−2014, and there was no difference in their detection probability due to count sequence. This suggests that greater precision in population estimates can be achieved if future surveys include repeat visits. No palila were detected outside the core survey area in 2013 or 2014, suggesting that most if not all palila inhabit the western slope during the survey period. Since 2003, the size of the area containing all annual palila detections do not indicate a significant change among years, suggesting that the range of the species has remained stable; although this area represents only about 5% of its historical extent. During 1998−2003, palila numbers fluctuated moderately (coefficient of variation [CV] = 0.21). After peaking in 2003, population estimates declined steadily through 2011; since 2010, estimates have fluctuated moderately above the 2011 minimum (CV = 0.18). The average rate of decline during 1998−2014 was 167 birds per year with very strong statistical support for an overall declining trend in abundance. Over the 16-year monitoring period, the estimated rate of change equated to a 68% decline in the population.
Status and trends of the land bird avifauna on Tinian and Aguiguan, Mariana Islands.
(2016-01-26) Camp, Richard; Pratt, Thane; Amidon, Fred; Marshall, Ann; Kremer, Shelly; Laut, Megan
Avian surveys were conducted on the islands of Tinian and Aguiguan, Marianas Islands, in 2008 by the U.S. Fish and Wildlife Service to provide current baseline densities and abundances and assess population trends using data collected from previous surveys. On Tinian, during the three surveys (1982, 1996, and 2008), 18 species were detected, and abundances and trends were assessed for 12 species. Half of the 10 native species—Yellow Bittern (Ixobrychus sinensis), White-throated Ground-Dove (Gallicolumba xanthonura), Collared Kingfisher (Todiramphus chloris), Rufous Fantail (Rhipidura rufifrons), and Micronesian Starling (Aplonis opaca)—and one alien bird—Island Collared-Dove (Streptopelia bitorquata)—have increased since 1982. Three native birds—Mariana Fruit-Dove (Ptilinopus roseicapilla), Micronesian Honeyeater (Myzomela rubratra), and Tinian Monarch (Monarcha takatsukasae)—have decreased since 1982. Trends for the remaining two native birds—White Tern (Gygis alba) and Bridled White-eye (Zosterops saypani)—and one alien bird—Eurasian Tree Sparrow (Passer montanus)—were considered relatively stable. Only five birds—White-throated Ground-Dove, Mariana Fruit-Dove, Tinian Monarch, Rufous Fantail, and Bridled White-eye—showed significant differences among regions of Tinian by year. Tinian Monarch was found in all habitat types, with the greatest monarch densities observed in limestone forest, secondary forest, and tangantangan (Leucaena leucocephala) thicket and the smallest densities found in open fields and urban/residential habitats. On Aguiguan, 19 species were detected on one or both of the surveys (1982 and 2008), and abundance estimates were produced for nine native and one alien species. Densities for seven of the nine native birds—White-throated Ground-Dove, Mariana Fruit-Dove, Collared Kingfisher, Rufous Fantail, Bridled White-eye, Golden White-eye (Cleptornis marchei), and Micronesian Starling—and the alien bird—Island Collared-Dove—were significantly greater in 2008 than 1982. No differences in densities were detected between the two surveys for White Tern and Micronesian Honeyeater. Three native land birds—Micronesian Megapode (Megapodius laperouse), Guam Swiftlet (Collocalia bartschi), and Nightingale Reed-Warbler (Acrocephalus luscinia)—were either not detected during the point-transect counts or the numbers of birds detected were too small to estimate densities for either island. Increased military operations on Tinian may result in increases in habitat clearings and the human population, which would expand human-dominated habitats, and declines in some bird populations would be likely to continue or be exacerbated with these actions. Expanded military activities on Tinian would also mean increased movement between Guam and Tinian, elevating the probability of transporting the brown tree snake (Boiga irregularis) to Tinian.
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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