Justification of Red List Category
This species qualifies as Vulnerable because it occupies a small and declining range, in which its population is severely fragmented and in decline, owing primarily to the effects of introduced species, including pathogens.
Population estimates for each subspecies are as follows: bryani c.2,500 birds in 1983; sandwichensis c.63,000 birds in 1983; and ridgwayi c.150,000 birds in 1976-1979 (Scott et al. 1986), giving a total population estimate of c.216,000 individuals.
Surveys in the Central Windward region of Hawai`i from 1977 to 2003 indicate that the species is stable at high elevations and declining at low elevations (Gorresen et al. 2005), and there is also evidence of a decline in the Ka`u region between 1976 and 2005 (Tweed et al. 2007). Its disappearance from Pohakuloa Training Area was recently noted (VanderWerf 2011), and declines have been detected in high elevation mamane-naio forests (E. VanderWerf in litt. 2011). Declines are projected to continue on the basis of ongoing habitat degradation and the threat of disease.
Chasiempis sandwichensis is endemic to Hawai`i in the Hawaiian Islands (USA) (VanderWerf et al. 2009). There are three recognised subspecies, but variation in appearance is clinal and there is broad overlap (VanderWerf 2011): C. s. bryani had an estimated population of c.2,500 birds in 1983, and may be declining; the other two subspecies had populations estimated at c.63,000 for C. s. sandwichensis and c.150,000 for C. s. ridgwayi in 1976-1979 (Scott et al. 1986). Surveys in the Central Windward region of Hawai`i from 1977 to 2003 indicate that the species is stable at most high elevation areas and declining at some low elevations (Gorresen et al. 2005), and there is also evidence of a decline in the Ka`u region between 1976 and 2005 (Tweed et al. 2007). Its disappearance from Pohakuloa Training Area was recently noted (VanderWerf 2011), and declines have been detected in high elevation mamane-naio forests (E. VanderWerf in litt. 2011).
Subspecies bryani occupies arid, mostly high-altitude mamane and mamane-naio woodland, whilst sandwichensis occurs in mesic habitats on western and south-western slopes, and ridgwayi is restricted to wet, eastern slopes (Pratt 1980, Scott et al. 1986, VanderWerf 1998). It feeds on insects and other invertebrates (Scott et al. 1986).
The habitat of bryani has been heavily browsed by feral ungulates and introduced grasses suppress regeneration and potentially increase the risk of fire (Scott et al. 1986). Diseases, such as avian pox and malaria, spread by mosquitoes, are a problem at low and middle elevations, increasing mortality and possibly preventing birds from nesting (E. VanderWerf in litt. 1999, VanderWerf et al. 2006). High prevalence in mosquito-borne diseases and local declines in the species's population are associated with high rainfall (VanderWerf 2001b, Gorresen et al. 2005, VanderWerf et al. 2006). It has been suggested that the species may also suffer increased mortality associated with infection by chewing lice (Phthiraptera) (Freed et al. 2008). It remains vulnerable to future catastrophic events such as hurricanes (E. VanderWerf in litt. 2012)
Conservation Actions Underway
For bryani, the removal of goats and sheep from Mauna Kea has been attempted, but ungulate numbers have not declined sufficiently to allow regeneration and so habitat degradation is continuing. Cats were controlled (E. VanderWerf in litt. 1999), but this has now ceased due to an end in funding (T. Pratt in litt. 2007). Habitat restoration and reforestation at mid and high elevations on Hawai`i is expected to benefit sandwichensis and ridgwayi (T. Pratt in litt. 2007). Fencing is underway on Mauna Kea to protect Palila Loxioides bailleui critical habitat by excluding ungulates, and this also should benefit the Hawaii Elepaio.
14 cm. Small monarch flycatcher that often cocks its tail. Adults have white tips to tail feathers, white rump, and white wing bars. Immatures are greyish-brown and have buffy wingbars (VanderWerf 2001a). Adult variable and sexually dimorphic, generally brown above with white underparts and variable amount of dark streaking below; male has black chin, female white (VanderWerf 2001a). Similar spp. Introduced Japanese Bush-warbler Cettia diphone duller with prominent eyebrow and no white markings. Voice Song a lively whistled eh-leh-PYE-o, given in series of four with emphasis on the third phrase (del Hoyo et al. 2006); calls include sharp chup, two-note squeak-it like dog's toy, and raspy chatter.
Text account compilers
Benstead, P., Derhé, M., Stattersfield, A., Stuart, T., Taylor, J.
Gorresen, M., VanderWerf, E., Woodworth, B., Pratt, T., Camp, R., Fretz, S.
BirdLife International (2021) Species factsheet: Chasiempis sandwichensis. Downloaded from http://www.birdlife.org on 16/10/2021. Recommended citation for factsheets for more than one species: BirdLife International (2021) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 16/10/2021.