Data Zone
Justification of Red List category
This species has an extremely small range. Its population size and extent of habitat are declining, probably as a result of the encroachment of avian malaria into higher elevations as temperatures increase due to climate change. For these reasons, it is listed as Critically Endangered.
Population justification
Trend justification
Surveys during 1980, 1995-1997 and 1997-2001 found an increasing trend in population densities (Scott et al. 1986; Simon et al. 2002; Camp et al. 2009). The population was estimated at 3,753 ± 373 individuals in 1980 (Scott et al. 1986) and 6,745 ± 1,546 individuals in 2001 (Camp et al. 2009). The population size has subsequently decreased rapidly (Paxton et al. 2018; Judge et al. 2019). In 2017, the population size was estimated at 1,768 (95% C.I. 1,193–2,411) individuals (Judge et al. 2019). The species's range has contracted by 61% since 1980, with range lost at lower elevations over 10-15 years prior to 2017 (Camp et al. 2009; Judge et al. 2019).
Based on the population estimates from 2001 and 2017 (Camp et al. 2009; Judge et al. 2019) and assuming exponential decline, the species's population size is estimated to have undergone a reduction of between 48 and 81% over the past three generations (14 years), with a best estimate of 68%. Threats are ongoing, so the species's population is assumed to continue to decline at a similar rate over the next three generations. A model of the impact of malaria encroachment under climate change on the species's range predicted that the species will lose 92.1% of its range between 1990–2010 and 2080–2100 (Fortini et al. 2015).
Palmeria dolei occurs on Maui in the Hawaiian Islands (U.S.A.) and is extinct on Moloka'i (last confirmed observations in 1907). On Maui, it remains only on the north-eastern slopes of Haleakala volcano (Camp et al. 2009, Judge et al. 2019).
It occurs in mesic 'Ōhi'a-koa and wet 'Ōhi'a forest from 1,100-2,300 m (99% above 1,500 m, mostly below 2,100 m). It primarily feeds on 'Ōhi'a nectar, also taking invertebrates, especially caterpillars. When 'Ōhi'a bloom is at its seasonal low, it feeds on subcanopy and understorey flowers and fruit (Berger 1972; Scott et al. 1986; P. Baker in litt. 1999; J. C. Simon in litt. 1999). All known nests have been in 'Ōhi'a trees (Berlin and VanGelder 1999). It raises 1-2 young per nest, usually nesting twice seasonally (November to June [Simon et al. 2001]), and has a relatively high success rate (J. C. Simon in litt. 1999; Simon et al. 2001). Adult survivorship is similarly high (Simon et al. 2001). Birds, perhaps especially immatures, may disperse to lower elevations (Berlin and VanGelder 1999).
Habitat destruction and modification and the rapid spread of disease-carrying mosquitoes in the lowlands are thought to be responsible for past declines. There has been extensive historic loss of forest within the species's range, through logging and clearance for agriculture.
The most significant long-term threat is Avian Malaria (Judge et al. 2019). The disease is transmitted by the introduced southern house mosquito Culex quinquefasciatus, and has been detected in the Akohekohe (Feldman et al. 1995). Both the Culex quinquefasciatus mosquito and the Plasmodium relictum parasite develop more easily at higher temperatures (LaPointe et al. 2010), and the resultant prevalence of malaria at lower elevations is thought to explain the species's recent range contraction at lower elevations (Judge et al. 2019). The species may be particularly vulnerable to mosquito-borne diseases, including avian malaria and avian pox, because it migrates altitudinally in response to varying 'Ōhi'a flowering physiology, potentially increasing exposure to mosquitoes at lower elevations (USFWS 2003). Increased temperatures associated with climate change are predicted to increase the prevalence of malaria at higher altitudes in the future (Freed et al. 2005). An analysis of the impact of a two degree Celsius temperature rise (as predicted by the end of this century) on the area of malaria-free forest in the Hanawi Forest found that the area where malarial infection is highly probable would increase from 40% to 63% (Benning et al. 2002). A model of the impact of malaria encroachment under climate change on the species's range predicted that the species will lose 92.1% of its range between 1990–2010 and 2080–2100 (Fortini et al. 2015).
From 1945 to 1995, the spread of feral pigs on Haleakala caused chronic habitat degradation (Loope and Medeiros 1995) and facilitated the spread of mosquitoes into remote rainforests (Pratt 1994). In Hanawi Natural Area Reserve, there was a 473% increase in pig activity, as indexed by ground-cover disturbance, during 1970-1997 (Rosa et al. 1998), and this reduced alternative food sources to 'Ōhi'a bloom (Berlin and VanGelder 1999). Predation by introduced rats, cats, Barn Owl (Tyto alba) and possibly small Indian Mongooses (Herpestes auropunctatus) is a further limiting factor (Berlin and VanGelder 1999, J. M. Scott in litt. 1999, J. C. Simon in litt. 1999, E. VanGelder in litt. 1999).
Recently introduced pathogens, Ceratocystis lukuohia and C. huliohia, both of which cause rapid 'Ōhi'a death (R.O.D.), or 'Ōhi'a Wilt, have spread rapidly across the Hawaiian islands and caused extensive mortality of 'Ōhi'a (Keith et al. 2015), which is an important food and nesting plant for Akohekohe. The effects of R.O.D. were noticed on Hawai'i by 2012, the disease was first identified in 2014 (Keith et al. 2015) and the Ceratocystis species involved were confirmed in 2018 (Barnes et al.). Ceratocystis sp. have now spread rapidly across much of the lowland forests on Hawai'i island, as well as on Kaua'i and O'ahu, with more than 600 km2 of forest affected by 2019 (Mortenson et al. 2016; Fortini et al. 2019; College of Tropical Agriculture and Human Resources 2020). Surveys of infected forest have found that an average of 25% of 'Ōhi'a trees were dead (Camp et al. 2019). Surveys in an infected area of forest found that the density of another Hawaiian honeycreeper, the Hawaii Amakihi (Chlorodrepanis virens), declined by 79% between 2003-2004 and 2016, following the infection of the forest with R.O.D. (Camp et al. 2019). In 2019, a single 'Ōhi'a tree was confirmed to be infected on Maui and was destroyed (College of Tropical Agriculture and Human Resources 2020). C. lukuohia appears to be associated with higher temperatures, and a model of its potential range across Hawaii under current climatic conditions suggested that it may not affect habitat at higher elevations on Maui where the Akohekohe occurs (Fortini et al. 2019), but climate change could facilitate its spread into higher elevations where it may impact the Akohekohe.
Climate change may also cause habitat shifts and increase the frequency of extreme weather events that could present further threats to the Akohekohe.
Conservation and Research Actions Underway
The species occurs in Haleakala National Park, Waikamoi Preserve and Hanawi Natural Area Reserve.
Research into captive breeding was attempted, and six individuals were hatched from late-stage wild eggs (USFWS 2003), but there are no individuals surviving in captivity (USFWS 2011). Studies have been carried out with the more common I'iwi (Drepanis coccinea) to investigate the feasibility of translocating the species (Becker et al. 2010). Research has been carried out using radio-tracking to determine juvenile and adult habitat selection, dispersal and seasonal movements (Maui Forest Bird Recovery Project 2013).
Cooperative management of the East Maui watershed includes fencing at c.1,070 m and removal of feral ungulates (Loope and Medeiros 1995, P. Baker in litt. 1999). In the Waikamoi Preserve, Hanawi Natural Area Reserve and Haleakala National Park, conservation practices combat the establishment of alien plants and, from the late 1980s, feral pigs have been controlled (Loope and Medeiros 1995, Simon et al. 1997). The Maui Forest Bird Recovery Project has been carrying out actions including cat and mongoose control, and community outreach and education (Mounce 2015). Rat control is underway in a portion of Hanawi NAR (USFWS 2011).
18 cm. Large honeycreeper with slightly downcurved, sharp bill and distinctive forward-curving crest of stiff, white feathers on forehead. Mostly black, streaked and spotted with orange-red and silvery-grey. Shaggy red-orange patch on hindneck, orange-buff eye-ring and short postocular stripe. Orange-buff thighs. Primaries and tail feathers tipped white. Sexes similar, but juvenile all sooty-grey with orange-buff eye-ring and very short, grey crest. Voice Song a variable series of low-pitched notes ah-gurk-gurk-gurk or ah-koh-heh-koh-heh and many other variations. Call a human-like upslurred whistle.
Text account compilers
Clark, J., Wheatley, H.
Contributors
Baker, P.E., Benstead, P., Bird, J., Camp, R., Derhé, M., Fretz, S., Gorresen, M., Harding, M., Isherwood, I., Mounce, H., North, A., Simon, J.C., Stattersfield, A., Stuart, T., Symes, A., VanGelder, E., VanderWerf, E., Woodworth, B. & Wright, L
Recommended citation
BirdLife International (2024) Species factsheet: Akohekohe Palmeria dolei. Downloaded from
https://datazone.birdlife.org/species/factsheet/akohekohe-palmeria-dolei 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.