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 small and declining at a rate exceeding 60% in ten years 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
Surveys in 2018 placed the population at 6,987 individuals (95% CI: 4,672–9,183) (Paxton et al. 2020), roughly equivalent to 3,100-6,100 mature individuals overall. Assuming declines have continued at the same rate (the most recent population estimate suggests an overall decline of c.57% within the time period 2008-2018 [Paxton et al. 2020]), this would now place the population in the band 2,200-4,400 mature individuals. There is also thought to be a small, isolated population in the Makaleha Mountains (Camp et al. 2009), however this is precautionarily assumed not to host mature individuals given the lack of recent records.
Trend justification
During 1968-1973, surveys estimated the population at 10,743 (± 970 standard error), with 76% of the population in the "west of Alaka`i" study compartment (USFWS 1983). Subsequent population estimates suggested that the population was greater than 15,000, possibly up to 20,000 birds, and increasing (Scott et al. 1986, Jacobi and Atkinson 1995, Lindsey et al. 1998). In 1992, Hurricane Iniki devastated forests throughout Kaua`i and all bird populations on the island appeared to have been drastically reduced (Pratt 1993, 1994). Subsequent population estimates suggested that this species had recovered (Jacobi and Atkinson 1995, Lindsey et al. 1998, P. Donaldson in litt. 1999, Foster et al. 2004), with the estimated population in the Alaka`i and Kôke`e areas increasing significantly to around 42,000 individuals in 2000 (Foster et al. 2004). However, estimates in 2012 indicated dramatic declines since 2000 of 91% in the core range and 98% in the periphery, with a resultant population estimate of only 6,519 individuals (95% CI: 4,844– 8,495; Paxton et al. 2016). The most recent population estimate of 6,987 individuals suggests an overall decline of c.57% within the time period 2008-2018 (Paxton et al. 2020), with declines exceeding 60% in interior forest. As such, the rate of decline is placed here in the range 55-70% within ten years.
This species is endemic to Kaua'i in the Hawaiian Islands (USA). It is common in the uplands including the Alaka`i Wilderness Preserve and especially in Kôke`e State Park, and an isolated population occurs in the Makaleha Mountains (USFWS 1983, Pratt 1993, Conant et al. 1998). Historically it ranged down to coastal elevations, as indicated by fossil evidence (P. Roberts in litt. 2007).
Originally, it occurred in native forests throughout Kaua'i. Today, it occurs above 600 m in `ohi`a forest, but is commonest in western koa-`ohi`a forest (USFWS 1983, Scott et al. 1986, Pratt et al. 1987, Lindsey et al. 1998). Preference for koa-`ohi`a may be attributable to koa itself (Conant et al. 1998), or the abundance of the introduced banana poka in the western parts of its range (Scott et al. 1985). It feeds by gleaning insects from trunks and branches (Pratt et al. 1987, Lindsey et al. 1998), and takes insects and nectar from flowers, apparently thriving on banana poka nectar (USFWS 1983, Conant et al. 1998, Lindsey et al. 1998). It is also an active excavator, hammering and flaking off bark to locate arthropods underneath (T. Snetsinger in litt. 2000).
Clearance of the lowland forests on Kaua`i removed most of the habitat used by this species (USFWS 1983, Lindsey et al. 1998). Current threats include predation from cats and rodents, disease (carried by introduced mosquitoes), ongoing habitat degradation by ungulates and invasive plants and (probably) competition from non-native birds (Lindsey et al. 1998, P. Baker in litt. 1999, J. M. Scott in litt. 1999, P. Roberts in litt. 2007, Paxton et al. 2018). Introduced mosquitoes, which spread avian pox and malaria, are now common at 900 m, and may be breeding as high as 1,200 m elevation (Glad and Crampton 2015). Climate change is projected to cause an increase in the elevation below which transmission of avian malaria occurs (Liao et al. 2017). Under a 2oC warming scenario and an increase in rainfall over high-elevation forests during the next 100 years, in keeping with climate model predictions for the region, the prevalence of malaria on Kaua`i is predicted to increase within the remaining habitat (Benning et al. 2002). The 17 oC isotherm, below which Plasmodium prevalence peaks, is predicted to shift upwards by around 300 m, decreasing the area of forest where Plasmodium prevalence is limited by 85% (Benning et al. 2002). Such changes are already associated with increased prevalence of avian malaria in this species (Atkinson et al. 2014) and the species' range is contracting (Paxton et al. 2016). High densities of this species in an area containing avian malaria has previously suggested some level of resistance (Foster et al. 2004), but the species is currently undergoing steep declines and considered vulnerable to extinction from increasing disease prevalence (Paxton et al. 2020, 2022). Feral pigs facilitate the spread of both alien plants and mosquitoes and, with other ungulates, continue to degrade native forests (Pratt 1994, VanderWerf 2012). Invasive plants have degraded significant portions of Kôke`e State Park and threaten the remainder of the habitat (P. Roberts in litt. 2007, Behnke et al. 2016). In addition to exacerbating the threat of introduced diseases, climate change is predicted to increase the geographic extent and intensity of habitat loss, invasive plants and non-native predators (Paxton et al. 2018). This species' restriction to Kaua`i and dependence on canopy species makes it vulnerable to catastrophic events such as hurricanes (P. Roberts in litt. 2007) which have caused substantial declines in the past (Pratt 1993, 1994). The emergence of the Ceratocystis wilt pathogen that causes rapid ‘ohi‘a death may also be a potential threat (Camp et al. 2019).
Conservation Actions Underway
Its habitat is partially protected from development by the Alaka`i Wilderness Preserve, the Kôke`e State Park (P. Roberts in litt. 2007), and several Natural Area Reserves (L. Crampton in litt. 2016). Portions of the Alaka`i Wilderness Preserve and the Hono O Na Pali reserve have been fenced (VanderWerf 2012). Removal of ungulates and invasive plants is ongoing. Weed control has been conducted by The Nature Conservancy and Kōke‘e Resource Conservation Program (VanderWerf 2012). Also, since 2014, expanding grids of Goodnature A24 rat traps have protected nests and breeding birds in the Alaka’i Wilderness Preserve (L. Crampton in litt. 2016). 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 (USFWS 2017, Miranda Paez et al. 2022).
Conservation Actions Proposed
Conduct research into its biology and limiting factors (Lindsey et al. 1998). 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 (USFWS 2017). Continue conducting periodic range-wide surveys to monitor status (VanderWerf 2012).
Protect core forest habitat (Paxton et al. 2018). Control introduced plants, predators, herbivores, competitors and mosquitoes, especially in the Alaka`i Wilderness Preserve (Scott et al. 1986, Lindsey et al. 1998). Implement a phased disease vector control programme (Paxton et al. 2018). Restore habitats (Paxton et al. 2018). Expand outreach to increase conservation attention and funds to the Kauai conservation crisis (Paxton et al. 2018).
11 cm. Small honeycreeper with medium-sized, sickle-shaped bill. Male olive-yellow, brighter on head and underparts, with dark grey lores. Bill dark on culmen shading to bluish-grey base of mandible. Female and juvenile similar but less bright. Similar spp. `Anianiau Magumma parva yellower, with much smaller bill and no black in lores. `Akeke`e Loxops caeruleirostris has shorter, bluish bill surrounded by dark mask, prominent yellow forehead and rump. Male Kaua`i Nukupu`u Hemignathus hanapepe yellow on head and breast, white below with all-black, thin bill, female nearly lacking yellow entirely. Voice Song a vigorous trill with short introductory note, sometimes on level pitch, sometimes descending. Typical call a sharp chirp. Also gives buzzy mewing note. Hints Bill much larger than in other `Amakihis, leading to many misidentifications as Nukupu`u. Easily seen at Koke`e.
Text account compilers
Vine, J.
Contributors
Baker, P.E., Crampton, L., Donaldson, P., Roberts, P., Scott, J.M., Snetsinger, T. & Woodworth, B.
Recommended citation
BirdLife International (2024) Species factsheet: Kauai Amakihi Chlorodrepanis stejnegeri. Downloaded from
https://datazone.birdlife.org/species/factsheet/kauai-amakihi-chlorodrepanis-stejnegeri on 24/12/2024.
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 24/12/2024.