Browsing by Author "Eben H. Paxton"
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Item Distribution and trends of endemic Hawaiian waterbirds, 1986–2023(2024-10-07) P. Marcos Gorresen; Richard J. Camp; Eben H. PaxtonThis study updates the status assessment of four endemic endangered Hawaiian waterbird species—ae‘o (Hawaiian stilt, Himantopus mexicanus knudseni), ‘alae ke‘oke‘o (Hawaiian coot, Fulica alai), ‘alae ‘ula (Hawaiian gallinule, Gallinula galeata sandvicensis), and koloa maoli (Hawaiian duck, Anas wyvilliana)—from 1986 to 2016 by incorporating new data from 2017–2023. State-space models, which account for biological and sampling variation, were fitted to estimate population sizes and trends from both core and non-core wetland survey sites. Long-term trends (1986–2023) largely show increasing populations for all four species, but recent short-term trajectories (2013–2023) are to a greater degree than previous analyses, predominantly negative, indicating accentuated declines in some island populations. Summer counts have declined relative to winter counts over the 38-year period, indicating potential changes in habitat availability and breeding patterns due to shifting rainfall patterns. Although negative trends were apparent in some non-core wetlands, our study underscores the importance of both core and non-core wetlands for waterbird populations.Item Post-Typhoon Mawar population counts of the endangered yǻyaguak (Mariana swiftlet) on Guam(University of Hawai'i at Hilo, 2024-05-15) Eben H. Paxton; P. Marcos Gorresen; Paul Cryan; Megan ParkerThe yǻyaguak (Mariana swiftlet, Aerodramus bartschi) is an endangered cave-roosting species native to Guam and southern Mariana Islands, Micronesia. The population on Guam has declined substantially over the last half century, likely due to the introduction of the brown treesnake (Boiga irregularis), but other factors have been proposed including habitat loss, pesticides, reduced food resources, and powerful storms. On May 24–25, 2023, Guam was hit by the category-4 Typhoon Mawar, which brought wide-spread destruction to the island. Approximately 6 weeks prior to the typhoon in April 2023, we conducted surveys of the three known colonies of yǻyaguak at Mahlac, Maemong, and Fachi caves. This survey provided a baseline population estimate prior to Typhoon Mawar’s landfall. In July 2023, we resurveyed the caves to estimate colony size and assess whether the cave colonies experienced significant declines in the immediate aftermath of the storm. In November 2023, we conducted our regularly scheduled biannual surveys which provided a longer-term assessment of potential impacts from the typhoon. Our counts indicated that in the immediate aftermath (~6 weeks) there was a 7–8% reduction in size of colonies compared to the April 2023 counts, but in November there were larger, 19–35% reductions in the cave colonies from pre-Mawar surveys. These results suggest that the long-term effects of the storm were more detrimental to the yǻyaguak populations than the immediate impacts if these colony size reductions are a result of the storm. Continued monitoring of the yǻyaguak cave colonies will allow for documenting the pace of recovery from the storm.