Justification of Red List Category
This species is classified as Endangered because it has a very small range in which some habitat is now being degraded through fire and grazing by feral ungulates, with the imminent threat of a new pressure posed by feral deer. It remains at risk from habitat degradation, disease and, in some areas, predation by introduced mammals.
In 1980, the early 1990s and 1997, the total population was estimated at c.35,000 birds, including fewer than 8,550 breeding pairs, therefore giving a maximum estimate of 17,100 mature individuals. In 2011, 52,729 and 57,921 individuals were estimated within 36.9 km2 of habitat on the northeastern slope of east Maui (Brinck et al. 2012). Surveys conducted to calculate this estimate excluded 13.7 km2 of known habitat and so overall numbers may be higher than this (Brinck et al. 2012). This is equivalent to roughly 35,153 - 38,614 mature individuals, and so is placed in the band 20,000-49,999 mature individuals.
The population is suspected to have declined over the past ten years owing to the degradation of koa forest in South Haleakala by feral goats (S. Fretz, R. Camp, E. Vanderwerf, M. Gorresen and B. Woodworth in litt. 2003) and a fire in PoliPoli State Park in 2007, which is thought to have impacted the local population (H. Mounce in litt. 2007). The overall rate of decline has not been estimated.
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 east, including Waikamoi Preserve to Kipahulu Valley (abundant), and Polipoli State Park and nearby areas south-west of Haleakala peak (Baker and Baker 2000) (no longer common, but exact status unsure [H. Mounce in litt. 2007]). Population densities decline below 1,600 m elevation: in 1980, surveys recorded none below 900 m (Scott et al. 1986) and, in 1997, there was an almost total absence below 1,480 m, with only 40 km2 of occupied good quality habitat above 1,525 m (Baker and Baker 2000). In 1980, the early 1990s and 1997, the total population was estimated at c.35,000 birds (Scott et al. 1986, Jacobi and Atkinson 1995, Baker and Baker 2000) (but <8,550 breeding pairs), suggesting overall stability, although the range has contracted in this time (Baker and Baker 2000). In 2002, it was reported that koa forest in South Haleakala was being degraded by feral goats, prompting suspicions of a population extirpation (S. Fretz, R. Camp, E. Vanderwerf, M. Gorresen and B. Woodworth in litt. 2003), and in 2007, a fire in PoliPoli State Park destroyed an area of the species's habitat and probably a proportion of the population (H. Mounce in litt. 2007). Surveys after the fire found some surviving birds, but the lack of baseline surveys before the fire has prevented an analysis of the impact on the population (H. Mounce in litt. 2007).
It inhabits dense, wet forests dominated by `ohi`a 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 size range is 0.86 ± 0.09 ha.
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. 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 response models indicate that this species is associated with forest interiors that are less damaged by feral pigs (Scott et al. 1986). A number of introduced mammals, birds and insects are potential predators and competitors. A fire at PoliPoli State Park in 2007 is thought to have impacted the local population (H. Mounce in litt. 2007). Invasive plant species such as strawberry guava (Psidium cattleianum) also 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
The core areas where this species reaches its highest population densities are within three protected areas: Waikamoi Preserve, Hanawi Natural Area Reserve and Haleakala National Park, where fencing and control of feral ungulates is already resulting in the slow regeneration of native `ohi`a forests (Loope and Medeiros 1995, Lepson and Freed 1997, Simon et al. 1997, USFWS and Hawai`i DLNR 1999). Habitat restoration within Nakula NAR on South Haleakala 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).Conservation Actions Proposed
Conduct further research into the effect of diseases (Baker and Baker 2000). Study its population dynamics and demography (Baker and Baker 2000). Protect habitat from feral ungulates and rodents (Baker and Baker 2000). Extend plant control to areas outside the three wildlife protection areas (Loope and Medeiros 1995). Encourage the regeneration of native high-elevation forests (Baker and Baker 2000). 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). Routinely monitor the East Maui watershed conservation programme (P. Baker in litt. 1999).
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 Hemignathus virens not as yellow (male) and has curved bill, more black in lores. Introduced Japanese White-eye Zosterops japonicus smaller, greenish above and adults have prominent white eye-ring. Japanese Bush-warbler Cettia 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
Benstead, P., Capper, D., Khwaja, N., Stattersfield, A., Stuart, T., Taylor, J., Derhé, M., North, A.
Gorresen, M., Woodworth, B., Fretz, S., Mounce, H., VanderWerf, E., Camp, R., Baker, P.E.
BirdLife International (2019) Species factsheet: Paroreomyza montana. Downloaded from http://www.birdlife.org on 17/11/2019. Recommended citation for factsheets for more than one species: BirdLife International (2019) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 17/11/2019.