Data Zone
Justification of Red List category
This species is classified as Endangered owing to its very small and contracting range where habitat degradation is ongoing. The population is thought to be declining and is highly susceptible to avian malaria, with climate change projected to cause an increase in the elevation below which regular transmission occurs.
Population justification
The total population size was estimated to number 74,997 ± 8,520 individuals in 1980, 168,702 ± 5,786 in 1992, 124,027 ± 12,663 in 2001 and 96,105 ± 10,014 in 2011 (Judge et al. 2021). The most recent population estimate in 2017 was 99,060 ± 9,510 individuals (95% CI 88,502–106,954) (Judge et al. 2021), roughly equivalent to 60,000-70,000 mature individuals.
Trend justification
Long-term trends indicate a 41% decrease in abundance since the highest estimate in 1992 (Judge et al. 2021). Population estimates indicate an increase in the 1990s followed by a decline over the 2000s, with the trend then appearing to level off in recent years (Judge et al. 2021), which could be due to the protection and restoration of large intact high elevation forests like The Nature Conservancy’s Waikamoi Preserve and Hanawi Natural Area Reserve (C. Warren in litt. 2020). Results were inconclusive when assessing the range-wide short-term trends in 2011-2017 (Judge et al. 2021), however trend assessments for the Haleakal? National Park survey region from 2000–2017 show evidence that the population is continuing to decline (Brinck 2020). Given that the threats are ongoing, the species is inferred to be declining overall.
Paroreomyza montana is endemic to Maui in the Hawaiian Islands, U.S.A. The nominate subspecies formerly occurred on Lana'i, but it became extinct around 1937. On Maui, it is now found only in two locations in the north- and east-facing slopes of Haleakalā, including Waikamoi Preserve to Kipahulu Valley. A second disjunct population exists in Kula Forest Reserve and nearby areas, in primarily non-native forest (Baker and Baker 2000, Judge et al. 2021). On Maui, they formerly existed on Mauna Kahalawai (West Maui) and the southern (or leeward) slopes of Haleakalā.
It inhabits dense, wet forests dominated by ʻōhiʻa trees, but occurs in a variety of other forest, scrub and savanna habitats dominated either by native or introduced plants. It feeds on invertebrates and nectar (Scott et al. 1986, Pratt et al. 1987). It lives in small family groups of 2-6 birds (Baker and Baker 2000). Mean home range size is 0.86 ± 0.09 ha (Warren et al. 2015). The species is found below 1,500 m but in reduced densities due to avian malaria, with most detections above 1,200 m (Judge et al. 2021).
Clearance of lowland forest has inevitably resulted in range contraction, but its absence from suitable habitat at lower elevations is attributed to the presence of disease-carrying mosquitoes. The primary threat to this species is introduced avian disease to which it is highly susceptible, particularly avian malaria (Plasmodium relictum). The population of the Maui ‘Alauahio is larger than the two other endemic Hawaiian honeycreepers left on Maui, likely due to its ability to adapt to non-native forests, its generalist diet and small home ranges, and its higher fecundity (Judge et. al 2021). However, climate change increasing the elevation below which regular transmission of avian malaria occurs (Atkinson et al. 2014, Fortini et al. 2015, Judge et al. 2021). Avian pox is an additional threat to the species (VanderWerf 2012). Feral ungulates, especially pigs, have also caused extensive habitat loss and degradation (Scott et al. 1986, Loope and Medeiros 1995, USFWS and Hawai`i DLNR 1999) and mosquitoes have followed the spread of feral pigs into upland areas (Loope and Medeiros 1995). Habitat degradation as a result of invasive plants, feral pigs and goats within the range is ongoing (Judge et al. 2021). A number of birds and insects are potential competitors, and rats are confirmed predators of eggs and nestlings (Baker and Baker 2020). Other predators may include Short-eared Owl (Asio flammeus), Barn Owl (Tyto alba), Small Indian Mongoose (Herpestes auropunctatus), and feral cats (Felis catus) (Baker and Baker 2020). Extreme weather events, like hurricanes and wildfires, amplified by climate change may also impact this species, especially the subpopulation in Kula Forest Reserve as recent events (i.e. 2007 fire and 2014 hurricane Iselle) have shown impacts to the forest habitat integrity (L. Berthold in litt. 2020). Invasive plant species such as strawberry guava (Psidium cattleianum) pose a threat through reduced habitat quality, though this species can nest and forage on some non-native plant species (VanderWerf 2012).
Conservation Actions Underway
This species has benefitted from conservation measured targeted at other threatened honeycreepers on the island (Baker and Baker 2020). The core areas where this species reaches its highest population densities are within three protected areas: Waikamoi Preserve, Hanawi Natural Area Reserve and Haleakalā National Park, where fencing and control of feral ungulates has resulted in the slow regeneration of native ʻōhiʻa forests (Loope and Medeiros 1995, Lepson and Freed 1997, Simon et al. 1997, USFWS and Hawai'i DLNR 1999). Control of invasive plants and predators is ongoing within the range (Baker and Baker 2020). Habitat restoration within Nakula Natural Area Reserve and other Leeward forests on South Haleakalā may provide new habitat areas in the future (Department of Land and Natural Resources 2015). Research conducted on home range size, combined with demographic and genetic data can be used to design effective translocation plans (Warren et al. 2015). Development of genetic tools to reduce transmission of avian malaria is ongoing. This includes transgenic or genetically modified mosquitoes that have reduced ability to transmit pathogens and also incompatible insect techniques, for example using a different strain of Wolbachia bacteria to produce males that cannot produce viable offspring (Judge et al. 2021, Miranda Paez et al. 2022).
Conservation Actions Proposed
Carry out surveys to obtain an up-to-date estimate of the population size. Study its population dynamics and demography (Baker and Baker 2000). Continue genetic research in disease immunity in Hawaiian honeycreepers (Paxton et al. 2018). Continue research in the fields of genomic technologies and genetically modified mosquitoes for disease control and their field application (Paxton et al. 2018). Monitor population trends through regular surveys.
Initiate landscape-scale control of predators (Judge et al. 2021). Implement a landscape-level mosquito control programme (Paxton et al. 2018). Extend habitat restoration to areas outside the three wildlife protection areas (Loope and Medeiros 1995). Encourage the regeneration of native high-elevation forests (Baker and Baker 2000, Judge et al. 2021). When possible, translocate the species to establish several widely distributed populations (Baker and Baker 2000), including on the leeward side of east Maui or mountains in west Maui (H. Mounce in litt. 2007); this likely cannot occur until mosquito control or eradication happens in these areas (C. Warren in litt. 2020).
11 cm. Small, straight-billed, warbler-like passerine. Male bright golden-yellow on face and underparts, olive-green on crown and upperparts. May show tiny fleck of black in lores. Bill dark above, pinkish-yellow below. Female similar in pattern but all colours muted, juvenile duller still. Similar spp. Hawai`i `Amakihi Chlorodrepanis virens not as yellow (male) and has curved bill, more black in lores. Introduced Mountain White-eye Zosterops japonicus smaller, greenish above and adults have prominent white eye-ring. Japanese Bush-warbler Horornis diphone grey-brown overall with pale underparts and never have yellow on face. Voice Song a lively whurdy-wheesee-whurdy-chick or a longer warble resembling song of introduced House Finch Carpodacus mexicanus. Call a sharp cheeck or chirk. Hints Forms nucleus of mixed-species flocks on Maui. Most accessible locality for observation is Hosmer Grove in Haleakala National Park.
Text account compilers
Vine, J.
Contributors
Baker, P.E., Berthold, L., Mounce, H. & Warren, C.
Recommended citation
BirdLife International (2024) Species factsheet: Maui Alauahio Paroreomyza montana. Downloaded from
https://datazone.birdlife.org/species/factsheet/maui-alauahio-paroreomyza-montana on 23/11/2024.
Recommended citation for factsheets for more than one species: BirdLife International (2024) IUCN Red List for birds. Downloaded from
https://datazone.birdlife.org/species/search on 23/11/2024.