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 declining and 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 1976-1983 estimated the population at c.12,500 individuals (Scott et al. 1986). In 2009, the total population was estimated at c.14,000 birds (Gorresen et al. 2009), roughly equivalent to 9,300 mature individuals overall, with 9,888 birds (95% CI: 6,115-14,974) occurring in Hakalau Forest National Wildlife Refuge (Kendall et al. 2022).
Trend justification
Trend analysis has previously indicated a density increase in Hakalau Forest National Wildlife Refuge in north windward Hawai‘i (Camp et al. 2010b, 2016) and the species was considered stable overall (USWFS 2020). However, a more recent analysis of annual population density estimates in this area showed an overall downwards trend in the time period 1987-2019 and in the most recent decade 2010-2019, with this region supporting 71% of the global population (Kendall et al. 2022). In the period 2010-2019, density across all strata (open forest, closed forest and pasture) decreased by approximately 20%, with density in closed forest alone declining by approximately 40% (Kendall et al. 2022). The ongoing rate of decline is therefore placed in the range 20-40% within ten years. Additionally, trend analysis has shown that density for central windward Hawai‘i is declining in intact native forest (Camp et al. 2010a), while trends are unclear for Ka‘? and populations in central Kona and Hual?lai regions are thought to be very small or nearly extirpated (Gorresen et al. 2009, USWFS 2020). Declines are predicted to continue given that the threats are ongoing. Given that the species is highly susceptible to avian malaria, climate change is likely to reduce the area of suitable remaining habitat and drive further declines through causing an increase in the elevation below which regular transmission occurs (USWFS 2020).
This species is endemic to Hawai`i in the Hawaiian Islands (U.S.A.), where it was formerly widespread, but now occurs as four disjunct populations in windward Hawai‘i, Ka‘ū, Kona, and Hualālai (USFWS 2020).
It occurs principally in wet and mesic koa-‘ōhi‘a forest mainly between 1,000 and 2,300 m, with the highest densities mainly between 1,500 and 1,900 m (Ralph and Fancy 1994) in old-growth forests (Lepson and Woodworth 2002). Historical and occasional recent sightings in dry mamane forest suggest that some individuals may move seasonally, or that a very small population may inhabit dry forest year-round (Scott et al. 1986, Snetsinger 1995-1996). It nests in koa trees as well as in tall ‘ōhi‘a trees, and the species has successfully bred in disturbed woodland (VanderWerf 1998). It forages for insects, spiders, and other invertebrates on large or medium-size branches, mostly on koa and ‘ōhi‘a, but also on pilo (Coprosma spp.), ‘ōlapa (Cheirodendron trigynum), naio, and kāwa‘u (Ilex anomala). The nesting season is from February-June (VanderWerf 1998, Woodworth et al. 2001). Most nests are open cups, but about 15 percent are placed in cavities or in bark crevices. The female builds the nest, incubates eggs, and broods nestlings. The male delivers food to the female on and off the nest. Both parents feed the young for approximately one month after fledging. They re-nest after failures and pairs have been documented raising two broods in a season. Nest success of the species is low (VanderWerf 1998), but adults have high annual survival (Woodworth et al. 2001). During the breeding season the species’ home range averages 4-7 hectares (10-17 acres) in size and a 10-20 meter (33-66 feet) territory around the nest is defended (VanderWerf 1998). Outside the breeding season, Hawai’i Creepers frequently join mixed-species foraging flocks (Hart and Freed 2003) and forage over home ranges that average 11 hectares (VanderWerf 1998).
The primary threat to this species is introduced avian disease to which it is highly susceptible, particularly avian malaria (Plasmodium relictum), causing it to have a limited distribution at higher elevations (Atkinson et al. 1995; Atkinson et al. 2000; Banko and Banko 2009). Climate change is projected to cause an increase in the elevation below which regular transmission of avian malaria occurs, reducing the area of suitable habitat and exacerbating declines (USFWS 2020). According to climate projections, due to increased rainfall and temperatures, high elevation areas for Hawaiian bird populations will only remain free of mosquitos to mid-century (Liao et al. 2015) and GIS simulation has shown that a 2 degrees Celsius increase would cause a c.100% decline in the land area where transmission is currently only periodic (Benning et al. 2002). Avian poxvirus is an additional threat, also transmitted by the non-native southern house mosquito (Culex quinquefasciatus) (VanderWerf 2012). The species may have declined in the past owing to habitat loss and degradation (Ralph and Fancy 1994, VanderWerf 1998), although its ability to breed in some types of disturbed forest suggests that habitat alteration is not the primary factor limiting its current distribution (VanderWerf 1998). Feral ungulates, particularly pigs, have severely degraded native forests and facilitate the spread of alien plants and disease-carrying mosquitoes (Scott et al. 1986, Pratt 1994). Nest-predation by introduced rodents and nest-site limitation are additional threats (Ralph and Fancy 1994, VanderWerf 1998). Birds are also negatively affected by competition with Japanese White-eye Zosterops japonicus (Freed and Cann 2009), and chewing lice are thought to be an additional threat (Freed et al. 2008). 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).
Conservation Actions Underway
The Hakalau Forest National Wildlife Refuge was established to protect some of the best remaining habitat for this and other threatened honeycreepers (Scott et al. 1986, Ralph and Fancy 1994). The species has become extinct in the montane sections of the Hawai`i Volcanoes National Park (T. Pratt in litt. 2007). However, in 2003, the Kahuku unit was added to the national park, incorporating much of the species' habitat in the Kau area (T. Pratt in litt. 2007). The fencing and eradication of feral goats began in the national park in 1971 (Stone and Loope 1987), and the removal of cattle, mouflon sheep and pigs from the Kahuku unit is expected to benefit the species (T. Pratt in litt. 2007). During the 1990s, efforts were made to reduce the feral pig population by Hawaiian conservation authorities and private landowners (Anderson and Stone 1993). Planting of koa and other native plants began in the early 1990s, and at the Kapapala Forest Reserve and the Pu`u Wa`awa`a Forest Bird Sanctuary, cattle have been removed and fences erected (USFWS 2006). The Zoological Society of San Diego is developing techniques for rearing birds from eggs and breeding them in captivity, including the Hawai`i Creeper, at the Keauhou Bird Conservation Center (USFWS 2006). 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 2020, Miranda Paez et al. 2022).
11 cm. Inconspicuous bark-picker with conical, very slightly downcurved bill. Adults dull grey-green, paler below with white chin and throat, pale grey bill, and dark grey mask from base of bill to behind eye. Juvenile similar but with pale face and white superciliary. Similar spp. Hawai`i `Amakihi Chlorodrepanis virens female and juvenile similar, but throat never white, darker bill and narrower, more curved, dark lores. Voice Song a rattling, descending trill. Call an upslurred sweet. Juveniles following adults utter chatter of irregularly spaced notes whi-whit, whi-whi-whit etc. Hints Still found in most high-elevation native forests but easily overlooked. Joins mixed-species flocks in late summer and autumn.
Text account compilers
Vine, J.
Contributors
Camp, R., Gorresen, M., Lepson, J., Pratt, T. & VanderWerf, E.
Recommended citation
BirdLife International (2024) Species factsheet: Hawaii Creeper Manucerthia mana. Downloaded from
https://datazone.birdlife.org/species/factsheet/hawaii-creeper-manucerthia-mana on 23/12/2024.
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 23/12/2024.