Pacific Island landbird monitoring annual report, Hawaii Volcanoes National Park, tract group 1 and 2, 2010

Judge, Seth; Guadioso, Jacqueline; Hsu, Bobby; Camp, Richard; Hart, Patrick

Hawaii Volcanoes National Park (HAVO) was surveyed for landbirds and landbird habitat from March through May, 2010. This information provides the first datum in the time-series of landbirds monitoring for long-term trends in forest bird distribution, density, and abundance. The entire survey area was comprised of eight tracts. Each was surveyed using point-transect distance sampling to calculate estimates of bird abundance and density. In addition to the permanent survey transects from past landbird surveys in these tracts, randomly generated point-transects were also surveyed, providing a split panel sampling design. Twenty-nine species were detected yielding 9,845 records (9,803 during counts). Of the 29 species, two-thirds were non-native (19 species) and 10 species were native. Half of the native birds were endangered species—the Hawaiian goose (Branta sandwicensis), Hawaiian hawk (Buteo solitarius), akiapolaau (Hemignathus munroi), Hawaii creeper (Oreomystis mana), and Hawaii akepa (Loxops coccineus). The native apapane (Himatione sanguinea) and Hawaii apapane (Hemignathus virens), and non-native Japanese white-eye (Zosterops japonicus) were detected throughout the tracts and had the highest relative abundances, whereas 10 species were detected less than 10 times and in only one or two tracts. Sufficient detections to allow density estimation were made for nine species (5 native and 4 non-native). Changes in species-specific densities by tract were assessed using two-sample z-tests in an equivalence testing framework to determine long-term trends. In general, most densities were not estimated well enough to obtain conclusive results. However, for those species and tracts that were conclusive most birds have increased with a few notable declines. For example, the Hawaii apapane and apapane increased across all tracts, and the Japanese white-eye increased in all tracts except Northwest Kahuku and Papa. The most striking change in the native birds was that omao (Myadestes obscurus), which was considered extirpated from the Southwest Flank of Mauna Loa since the 1970s was detected in the high elevation tracts (Northwest Kahuku and Papa) of the region. Conversely, iiwi declined in the Northwest Kahuku tract and omao declined in the Olaa tract. Lastly, there was relatively little difference between the quantile distributions of the fixed and random transects (D=0.0568), thus, the fixed transects appear to be a random sample and representative of the larger population.

Pacific Island landbird monitoring annual report, Hawaii Volcanoes National Park, tract group 1 and 2, 2010

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