Justification of Red List Category
This species is classified as Critically Endangered owing to an extremely rapid decline in population size over the last ten years. Urgent action is required to halt the decline of this species, which until relatively recently was considered not uncommon.
The most recent population estimate is from 2012 when the number of individuals was estimated at 945 (460-1,547, 95% CI) (Paxton et al. 2016). This equates to approximately 310-1,000 mature individuals.
It was common throughout upper elevation forests in the late 19th century and was thought to be stable at c.20,650 individuals up until the mid-1990s, although its habitat declined in extent over this time period. However, in 2000, surveys estimated that the population was 7,839 ± 704 individuals, which has since decreased to 5,669 ± 1,003 individuals in 2005, 3,536 ± 1,030 in 2007 (VanderWerf 2007) and 945 individuals (460-1,547, 95% CI) in 2012 (Paxton et al. 2016). Thus the population is estimated to have declined very rapidly over the last ten years, and is expected to decline extremely rapidly over the next ten years.
The species is endemic to Kaua`i in the Hawaiian Islands (U.S.A.). It was common throughout upper elevation forests in the late 19th century and was thought to be stable at c.20,650 individuals up until the mid 1990s, although its habitat declined in extent over this time period (USFWS 1983, Scott et al. 1986, Lepson and Pratt 1997, S. Fretz et al. in litt. 2003). However, in 2000, surveys indicated that the population had decreased to 7,839 ±704 individuals, which dropped to 5,669 ± 1,003 individuals in 2005, 3,536 ± 1,030 in 2007 and 945 individuals (460-1,547, 95% CI) in 2012 (Paxton et al. 2016). Even allowing for the large error estimates this indicates a dramatic decline (Holmer 2007, D. Kuhn per Holmer 2007, D. Pratt per Holmer 2007, VanderWerf 2007). It occurs at the highest density in the remote Alaka`i region, especially the southeastern part of this region (Behnke et al. 2016), and also occurs in the upper Waimea and Koke`e regions; an isolated population persisted in the Makaleha Mountains until at least the early 1970s (Scott et al. 1986, Lepson and Pratt 1997). In the core of its range its presence is associated with large trees and native shrub cover (Behnke et al. 2016).
It inhabits wet `ohi`a, `ohi`a/olapa and diverse mesic forest, appearing to tolerate considerable habitat disturbance if sufficient `ohi`a remains (but see Behnke et al. 2016, who found lower occurrence of this species in areas of smaller `ohi`a and greater invasion by non native plants). It is found at 1,050-1,600 m, mostly above 1,100 m, and apparently never occurs in lowland forests. It feeds primarily on spiders and insects, taking nectar very rarely. Breeding occurs at least in March -June, and possibly February; all known nests have been in `ohi`a trees (Lepson and Pratt 1997, Hammond et al. 2015, Kauai Forest Bird Recovery Project, unpubl. data). Mean nest height for ‘Akeke‘e is 11.1 + 2.3 m SD (Hammond et al. 2015).
Development has reduced habitat availability in the Koke`e region, while the spread of exotic plants and feral ungulates is degrading remaining areas (Loope and Medeiros 1995, Lepson and Pratt 1997, VanderWerf 2012). Avian pox and malaria probably cause mortality because introduced mosquitoes (vectors for these diseases) are now common at 900 m, and may breed at 1,200 -1, 400 m (Herrmann and Snetsinger 1997, Lepson 1997, Lepson and Pratt 1997, Glad and Crampton 2015). There is concern that rising average temperatures could allow mosquitoes to survive at higher elevations and increase the exposure of birds to disease (Holmer 2007). A small increase in temperature is predicted to eliminate much of the mosquito-free zone on Kaua`i (U.S. Geological Survey per Holmer 2007) and a recent study has found evidence of this. Over the past two decades there has been a significant increase in the prevalence of avian malaria across the altitudinal range of the Alaka’i Plateau, which coincides with increasing air temperatures and changing patterns of precipitation and streamflow, which in turn support increased transmission of the disease (Atkinson et al. 2014). During this time period, prevalence of malaria remained very low in the few ‘Akeke’e individuals sampled, which may indicate high susceptibility to this disease (Atkinson et al. 2014). It is predicted that by 2100, there will be no “climatically-suitable” habitat left for this species on Kauai (Fortini et al. 2015). Food resources may be limited by alien wasps and ants which greatly reduce populations of native arthropods (Lepson and Pratt 1997). Introduced birds may also be competitors and introduced predators (particularly rats) probably cause some mortality (Lepson and Pratt 1997). However, Hammond et al. (2015) observed no predation by rats on the eight nests they monitored, although two nests failed due to failure of the eggs to hatch. Adverse weather may be a significant limiting factor, e.g. prolonged, heavy rains which can result in nesting failure and cause massive mortality among fledglings and juveniles (Lepson and Pratt 1997). Two recent hurricanes resulted in serious damage to Kaua`i's forests (Pratt 1994). ‘Akeke’e appear to avoid, to some extent, areas that have suffered more hurricane damage, and thus have few, large trees; and areas that have been heavily invaded by weeds (Behnke et al. 2016).
Conservation and Research Actions Underway Some of the current range is protected by Alaka`i Wilderness Preserve, Hono O Nā Pali Natural Area Reserve (NAR) and, to some extent, by Koke`e State Park. Portions of the Preserve have been/are being/will be included in ungulate proof fences in the next five years and post fence-completion, ungulates will be eradicated from these areas. Hono o Nā Pali NAR has already been fenced and ungulate, cat, and rodent control is ongoing within it (The Garden Island 2016, L. Crampton, pers. obs). In 2010 ‘Akeke’e was added to the endangered species list (Foote 2010). In April 2007, the Hawaii Department of Land and Natural Resources began to conduct population surveys of forest birds on Kaua`i to verify anecdotal evidence of a recent crash in the species's numbers (Holmer 2007). A captive breeding programme was started in 2015, as a collaboration between Kauai Forest Bird Recovery Project, State Department of Land and Natural Resources' Division of Forestry and Wildlife, U.S. Fish and Wildlife Service - Pacific Islands Fish and Wildlife Office and San Diego Zoo Global (Buley 2015, L. Crampton et al. in litt. 2015). Eggs are harvested from wild nests and the chicks hatched at San Diego Zoo Global's facilities in Hawaii (Buley 2015). The captive population currently numbers four birds (B. Masuda, pers. comm). Rodent control with GoodNature A24 self-resetting traps has also been initiated in the Halehaha area, with preliminary results suggesting rat numbers have declined (Elsel 2016, L. Crampton et al. in litt. 2015, pers. comm.). An experimental larval mosquito control programme will be initiated in Kawaikoi Stream of the NAR in 2016 (L. Crampton, pers. comm).
11 cm. Small, finch-like bird with notched tail and conical bill with slightly crossed tips (hard to see in the field). Male basically olive-green above, yellow below, with black mask surrounding bill to behind eye. Yellow forehead, forecrown and rump. Pale blue bill sometimes with dark tip. Female similar except colours muted and black mask less extensive. Similar spp. All other little green birds on Kaua`i (Kaua`i `Amakihi Hemignathus kauaiensis, `Anianiau H. parvus and introduced Japanese White-eye Zosterops japonicus) have dark rumps. Kaua`i Nukupu`u H. lucidus hanapepe has yellowish rump, but is much larger with longer black bill. Voice Songs are lively trills that shift pitch and speed. Call a piercing, upslurred szeet. Hints Feeds almost exclusively in terminal leaf clusters of ohi`a trees (not in flowers). Can be seen on trails east of Koke`e.
Text account compilers
Stattersfield, A., Stuart, T., Symes, A., Taylor, J., Wright, L, Benstead, P., Derhé, M., Ashpole, J, Hermes, C., Isherwood, I., Mahood, S., North, A., Capper, D.
Crampton, L., Vetter, J., Behnke, L., Paxton, E., Costantini, M., Roberts, P., Camp, R., VanderWerf, E., Fretz, S., Pejchar, L., Woodworth, B., Laut, M., Gorresen, M., Morrey, S.
BirdLife International (2019) Species factsheet: Loxops caeruleirostris. 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.