Evaluating the risk of avian disease in reintroducing the endangered Kiwikiu (Maui Parrotbill: Pseudonestor xanthophrys) to Nakula NAR, Maui, Hawai‘i

Warren, Christopher
Berthold, Laura
Mounce, Hanna
Foster, Jeffrey
Sackett, Loren
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Pacific Cooperative Studies Unit
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Avian malaria and other introduced diseases have had profound negative effects on Hawaiian honeycreepers, contributing to numerous extinctions and severely limiting the ranges of the remaining species. These diseases, concordant with habitat loss, are thought to restrict many species to narrow ranges at high elevations where cooler climates restrict reproduction of both the malaria parasite, Plasmodium relictum, and its mosquito vector, Culex quinquefasciatus. The Kiwikiu (Maui Parrotbill, Pseudonestor xanthophrys) is a critically endangered honeycreeper that formerly existed throughout Maui and Moloka‘i but now occupies roughly 30 km2 above 1400 m above sea level (asl) on the windward slopes of Haleakalā volcano. The species is thought to be highly susceptible to avian malaria based on its limited range and reported mortality in related species. The primary conservation action proposed for Kiwikiu is to expand the species’ range by reintroducing Kiwikiu to high elevation native forests on the south-facing leeward slope of Haleakalā. As part of an assessment of the suitability of the proposed release site, Nakula Natural Area Reserve, we sought to evaluate the risk of avian disease (i.e., avian malaria and pox) to the future Kiwikiu population. To do this, we trapped adult mosquitoes and surveyed for larvae throughout the release area in 2015–2016. We also tested blood samples from common bird species in Nakula using quantitative polymerase chain reaction analyses to estimate disease prevalence within the current bird population at the release site. To compare disease prevalence to habitat currently occupied by Kiwikiu, we also trapped mosquitoes and tested avian blood samples from common species in The Nature Conservancy’s Waikamoi Preserve in 2016. Unexpectedly, we captured adult and larval C. quinquefasciatus at much higher rates in Nakula than those reported from similar locations at comparable elevations (1530-1620 m asl) throughout Hawai‘i but did not capture C. quinquefasciatus in Waikamoi (1675-1700 m asl). Although leeward slopes receive far less rainfall than windward slopes, the drainages in Nakula contain small pools of water that can provide suitable breeding habitat for the mosquitoes. The frequency of high-flow periods in streams in Waikamoi may regularly “flush out” pools, reducing larval habitat. In contrast, the warmer temperatures and long periods between high-flow events may allow mosquitoes to persist year-round in Nakula. In contrast to mosquito capture rates, analysis of blood samples revealed similar or lower rates of avian malaria in two common honeycreeper species in Nakula compared to similar sites. We also found several individuals of two common honeycreeper species (i.e. Hawaiʻi ʻAmakihi [Chlorodrepanis virens] and ʻIʻiwi [Drepanis coccinea]) captured above 1900 m asl in Waikamoi to be positive for avian malaria. These results suggest that 1) although the persistence of mosquitoes represents an increased risk of infection in Nakula, the Plasmodium parasite may still be physiologically limited by environmental conditions at the release site, 2) the management of mosquitoes (e.g. biopesticides) is advisable to reduce infection risk, and 3) Kiwikiu may be at higher risk in its current range than previously considered. While creating a second population of Kiwikiu in Nakula is critical to safeguarding this species from extinction, mitigating the threat of avian malaria on a larger scale will be the only way to achieve island-wide recovery.
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avian malaria, Mosquitoes--Larvae, Mosquitoes as carriers of disease, Plasmodium relictum, Culex quinquefasciatus, Hawaii--Maui, translocation
Warren, C.C., L.K. Berthold, H.L. Mounce, J.T. Foster, L.C. Sackett. 2019. Evaluating the risk of avian disease in reintroducing the endangered Kiwikiu (Maui Parrotbill: Pseudonestor xanthophrys) to Nakula NAR, Maui, Hawai‘i. Pacific Cooperative Studies Unit Technical Report #201. University of Hawai`i at Mānoa, Department of Botany. Honolulu, HI. 50 pages.
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