Browsing by Author "Genz, Ayesha S."
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Item 2017-2018 Palila abundance estimates and trend(2018-12-25) Genz, Ayesha S.; Brinck, Kevin W.; Camp, Richard J.; Banko, Paul C.The palila (Loxioides bailleui) population was surveyed annually from 1998–2018 on Mauna Kea Volcano to determine abundance, population trend, and spatial distribution. In the latest surveys, the 2017 population was estimated at 1,177−1,813 birds (point estimate: 1,461) and the 2018 population was estimated at 778−1,420 (point estimate: 1,051). Only two palila were detected outside the core survey area during a mountain-wide survey in 2017, suggesting that most, if not all, palila inhabit the western slope during the annual survey period. Since 1998, the size of the area containing palila detections on the western slope did not show a significant change, 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] = 0.20). After peaking in 2003, population estimates declined steadily through 2011; since 2010, estimates have continued to decline at a slower rate. The average rate of decline during 1998−2018 was 168 birds per year with very strong statistical support for an overall declining trend in abundance. Over the 21-year monitoring period, the estimated rate of change equated to a 76% decline in the population.Item 2019–2021 Palila abundance estimates and trend(2022-01-24) Genz, Ayesha S.; Brinck, Kevin W.; Asing, Chauncey K.; Berry, Lainie; Camp, Richard J.; Banko, Paul C.The palila (Loxioides bailleui) population on Mauna Kea Volcano, Hawai‘i Island, was estimated from annual surveys in 2019−2021, and a trend analysis was performed on survey data from 1998−2021. The 2019 population was estimated at 1,030−1,899 birds (point estimate: 1,432), the 2020 population was estimated at 964−1,700 birds (point estimate: 1,312), and the 2021 population was estimated at 452−940 birds (point estimate: 678). Since 1998, a visual inspection of the size of the area containing palila detections on the western slope based on the minimum/maximum elevations has not shown a substantial change, indicating that the range of the species has remained stable; although this area represents only about 5% of its historical extent. During 1998−2005, palila numbers fluctuated between 4,000 and 6,000, followed by a steep decline. After 2010, palila estimates stabilized around an abundance of 2,000 with a much slower rate of decline. The decline during 1998−2021 was on average 229 birds per year with very strong statistical support for an overall downward trend in abundance. Over the 23-year monitoring period, the estimated rate of change equated to an 89% decline in the population.Item 2021 Tinian Island forest bird abundance estimates(2022-05-26) Camp, Richard J.; Bak, Trevor; Genz, Ayesha S.The U.S. Navy, through Micronesian Environmental Services, surveyed landbirds in the Military Lease Area on Tinian Island in May and June 2021 using point-transect distance sampling methods. There were 2,074 individuals of 14 species detected during 123 point counts. Six species were detected during >50% of the counts and were observed at relatively high abundances, while eight species occurred at <50% of the counts and were uncommon to rare. Densities of native landbirds in the Military Lease Area ranged from the uncommon Mariana kingfisher (Todiramphus albicilla) at 0.46 birds/ha (95% confidence interval [CI] = 0.33–0.63) to the very abundant bridled white-eye (Zosterops conspicillatus) at 102.63 birds/ha (95%CI = 86.70–122.91). Most distances recorded during the 2021 Military Lease Area survey were rounded to distance intervals of 0 and 5. Measuring exact distances of detected animals is preferable to collecting distances grouped into bins or rounding. Direct comparison with previously published estimates was not possible because of changes in the sampling frame; however, densities of six species were greater, two were smaller, and one was similar to the 2008 survey estimates for the Hagoi, Diablo, and Masalog regions. Our findings indicate that the landbird community in the Military Lease Area appears to be dynamic and resilient.Item Forest bird populations at the Big Island National Wildlife Refuge Complex, Hawai‘i(2022-04-13) Kendall, Steven J.; Rounds, Rachel A.; Camp, Richard J.; Genz, Ayesha S.Endemic Hawaiian forest birds have experienced dramatic population declines. The Big Island National Wildlife Refuge Complex (BINWRC) was created for conservation of endangered Hawaiian forest birds and their habitats. Surveys have been conducted at two units of BINWRC to monitor forest bird populations and their response to management actions. We analyzed survey data from 1987 to 2019 at the Hakalau Forest Unit (HFU) and from 1995 to 2019 at the Kona Forest Unit (KFU). We analyzed three strata at HFU: open-forest, closed-forest, and pasture, and two strata at the KFU: upper (>1524 m elevation) and lower (<1524 m). In all years, ‘i‘iwi (Drepanis coccinea), ‘apapane (Himatione sanguinea), and Hawai‘i ‘amakihi (Chlorodrepanis virens virens) were the most abundant species at HFU. The three endangered forest bird species, Hawai‘i ‘ākepa (Loxops coccineus), ‘alawī (Loxops mana, also known as Hawai‘i creeper) and ‘akiapōlā‘au (Hemignathus wilsoni), had much lower densities. The most abundant species at KFU was ‘apapane, followed by Hawai‘i ‘amakihi and warbling white-eye (Zosterops japonicus) at much lower densities. At HFU we found a continuation of several trends observed in previous analyses from 1987–2012, with most species’ trends upward in pasture stratum, stable in the open-forest stratum, and downward in the closed-forest stratum. However, when we looked at the most recent decade at HFU, more species were showing downward trends in all three strata. At KFU results were mixed, with more species’ trends downward in the upper stratum and more species’ trends upward in the lower stratum. Populations of endangered forest species were either locally extirpated at KFU or in numbers too low to reliably estimate population densities. Both units in the BINWRC are important for conservation of forest birds on Hawai‘i Island, and our results show that HFU supports the majority of the three endangered forest bird species found on Hawai‘i Island. Our analysis also shows the importance of continuous monitoring and timely analysis to track forest bird populations. With the additional data provided by continued surveys, we determined conclusive population trends for species whose trends were previously inconclusive. Knowing current population densities, abundances, and trends allows managers to evaluate and adapt management actions to support forest bird conservation at the BINWRC.Item Hawai`i forest bird monitoring database: Database dictionary(2017-09-15) Camp, Richard J.; Genz, Ayesha S.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.