Chasiempis sandwichensis Stejneger, 1988 — Sibley and Monroe (1990, 1993)
Chasiempis sandwichensis Stejneger, 1988 — Stotz et al. (1996)
Chasiempis sandwichensis Stejneger, 1988 — BirdLife International (2004, 2008)
||del Hoyo, J., Collar, N.J., Christie, D.A., Elliott, A., Fishpool, L.D.C., Boesman, P. and Kirwan, G.M. 2016. HBW and BirdLife International Illustrated Checklist of the Birds of the World. Volume 2: Passerines. Lynx Edicions and BirdLife International, Barcelona, Spain and Cambridge, UK.
||14 cm. Small monarch flycatcher that often cocks its tail. Adults have white tips to tail feathers, white rump, and white wing bars. Immatures have buffy or rufous wingbars (VanderWerf 2001). Adult brown above, white below with brownish streaks on breast, and with black chin irregularly blending into white throat. Similar spp. Introduced Japanese Bush-warbler Cettia diphone duller with prominent eyebrow and no white markings. Introduced juvenile White-rumped Shama Copsychus malabaricus larger, darker above, with dark spots on breast. Voice Song a lively whistled eh-leh-PYE-o, often given in series (del Hoyo et al. 2006); calls include sharp chup, two-note squeak-it like dog's toy, and raspy chatter.
|Red List Category & Criteria:
||Butchart, S. & Symes, A.
||Camp, R., Fretz, S., Gorresen, M., Pratt, T., VanderWerf, E. & Woodworth, B.
||Benstead, P., Derhé, M., Stattersfield, A., Stuart, T., Taylor, J. & North, A.
This species qualifies as Endangered because it has a very small and severely fragmented population, occupying a very small and declining range. Its population is suspected to be in decline owing to the effects of introduced species and declines in the extent and quality of habitat.
|Previously published Red List assessments:|
- 2012 – Endangered (EN)
- 2011 – Endangered (EN)
- 2008 – Not Recognized (NR)
- 2004 – Not Recognized (NR)
- 2000 – Not Recognized (NR)
- 1994 – Not Recognized (NR)
- 1988 – Not Recognized (NR)
|Range Description:||Chasiempis ibidis is endemic to O`ahu in the Hawaiian Islands (USA) (VanderWerf et al. 2009). It had an estimated population of 1,261 birds (95% CI=1, 205 - 1, 317), restricted to c.52 km2 in the Ko`olau and Wai`anae mountains, consisting of about 477 breeding pairs and 307 single males (Vanderwerf et al. 2013). This is only 25% of the range occupied in c.1975, and less than 4% of the presumed prehistoric range (VanderWerf et al. 2001). The O'ahu 'Elepaio has declined in abundance by about 50% since the 1990s, when the population was estimated to be about 1, 974 birds (VanderWerf et al. 2001). The genetically effective population size may be even lower because of the fragmented distribution (VanderWerf et al. 2001, 2013). The species has continued to decline over much of its range, particularly in the Wai`anae mountains, where only 300 birds were found in 2006-2010 (VanderWerf et al. 2011a). Surveys are underway in the Koolau Mountains to provide a complete update of current status (E. VanderWerf in litt. 2012).|
United States (Hawaiian Is.)
|♦ Continuing decline in area of occupancy (AOO):||Yes|
|♦ Extreme fluctuations in area of occupancy (AOO):||No||♦ Estimated extent of occurrence (EOO) - km2:||1100|
|♦ Continuing decline in extent of occurrence (EOO):||Yes||♦ Extreme fluctuations in extent of occurrence (EOO):||No|
|♦ Continuing decline in number of locations:||Yes|
|♦ Extreme fluctuations in the number of locations:||No||♦ Lower elevation limit (metres):||200|
|♦ Upper elevation limit (metres):||800|
|Range Map:||Click here to open the map viewer and explore range.|
|Population:||The total population was estimated at 1,261 mature individuals (95% CI=1, 205 - 1, 317) following surveys conducted from 2011-2012 (VanderWerf et al. 20013), consisting of about 477 breeding pairs and 307 single males. This total includes 592 males (95% CI= 554-630) and 369 females in the Ko'olau Mountains and 192 males and 84 females in the Wai' anae Mountains (VanderWerf et al. 2011, 2013).|
Trend Justification: Surveys conducted in the 1990s produced evidence that the species had declined by more than 75% since 1975 and by approximately 96% since the arrival of humans (VanderWerf et al. 2001). The species's population is still in decline owing to the effects of disease, introduced species and ongoing habitat loss and degradation. Bayesian modelling demonstrate rapid population collapse for this species (Aagaard et al. 2016). Surveys in 2006-2010 showed that the number of birds in the Waianae Mountains, which had supported half the population, had declined to only 300 birds (VanderWerf et al. 2011a).
|Current Population Trend:||Decreasing|
|♦ Number of mature individuals:||1261||♦ Continuing decline of mature individuals:||Yes|
|♦ Extreme fluctuations:||No||♦ Population severely fragmented:||Yes|
|♦ No. of subpopulations:||2-100||♦ Continuing decline in subpopulations:||Yes|
|♦ Extreme fluctuations in subpopulations:||No||♦ All individuals in one subpopulation:||No|