Justification of Red List Category
This species qualifies as Vulnerable because it has a very small range, occupying a small area of upland forest on one island, where it is at risk from the effects of exotic taxa. Although habitat is being degraded within its range, it apparently benefits from the introduction of banana poka and is able to utilise a broad range of habitat types.
The population in the Alaka'i and Koke'e areas alone was estimated at 6, 519 individuals (95% CI: 4,844– 8,495) in 2012.
The species's population in the Alaka`i and Koke`e areas increased significantly from around 11,000 individuals in 1973 to around 42,000 individuals in 2000 (Foster et al. 2004). The entire population is thus thought to be increasing.
Hemignathus kauaiensis 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). 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, the most recent 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. submitted).
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 primarily threats introduced by humans, such as cats and rodent predators, 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). Increased temperatures and changes to altitudinal rainfall and stream scouring patterns anticipated as climate change progresses, have already led to increased disease prevalence within remaining habitat (Atkinson et al. 2014). High densities of this species in an area containing avian malaria suggests some level of resistance (Foster et al. 2004). The restricted range of this species and its dependence on canopy species makes it vulnerable to catastrophic events such as hurricanes (P. Roberts in litt. 2007).
Conservation Actions Underway
Conservation Actions Proposed
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 H. parvus 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 H. lucidus 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
Benstead, P., Derhé, M., Isherwood, I., Stattersfield, A., Stuart, T., Taylor, J. & North, A.
Baker, P.E., Camp, R., Donaldson, P., Fretz, S., Gorresen, M., Leonard, D., Roberts, P., Scott, J., Snetsinger, T., VanderWerf, E., Woodworth, B., Crampton, L. & Costantini, M.
BirdLife International (2019) Species factsheet: Chlorodrepanis stejnegeri. Downloaded from http://www.birdlife.org on 16/09/2019. Recommended citation for factsheets for more than one species: BirdLife International (2019) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 16/09/2019.