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Chasiempis ibidis

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Taxonomy [top]

Kingdom Phylum Class Order Family
ANIMALIA CHORDATA AVES PASSERIFORMES MONARCHIDAE

Scientific Name: Chasiempis ibidis
Species Authority: Stejneger, 1988
Common Name(s):
English – Oahu Elepaio
Synonym(s):
Chasiempis sandwichensis Sibley and Monroe (1990, 1993)
Chasiempis sandwichensis Stotz et al. (1996)
Chasiempis sandwichensis BirdLife International (2004, 2008)
Taxonomic Notes: Chasiempis sandwichensis has been split into C. sandwichensis, C. sclateri and C. ibidis following AOU (2010).

Assessment Information [top]

Red List Category & Criteria: Endangered B1ab(i,ii,iii,iv,v) ver 3.1
Year Published: 2012
Date Assessed: 2012-05-01
Assessor(s): BirdLife International
Reviewer(s): Symes, A. & Butchart, S.
Contributor(s): Camp, R., Fretz, S., Gorresen, M., Pratt, T., VanderWerf, E. & Woodworth, B.
Facilitator/Compiler(s): Benstead, P., Derhé, M., Stattersfield, A., Stuart, T. & Taylor, J.
Justification:
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.

Geographic Range [top]

Range Description: Chasiempis ibidis is endemic to O`ahu in the Hawaiian Islands (USA) (VanderWerf et al. 2009). It had an estimated population of 1,973birds in 1992-2000, restricted to c.55 km2 in the Ko`olau and Wai`anae mountains, and including six isolated populations of 50-500 birds and several others of 10 or fewer (VanderWerf et al. 1997, VanderWerf 1998, VanderWerf et al. 2001). 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 breeding population was estimated to be smaller, at c.1,770 birds, owing to a male-biased sex-ratio (VanderWerf et al. 2001, USFWS 2006). The genetically effective population size may be even lower because of the fragmented distribution (VanderWerf et al. 2001). 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).
Countries:
Native:
United States
Range Map: Click here to open the map viewer and explore range.

Population [top]

Population: The breeding population was estimated at 1,768 mature individuals following surveys conducted in the 1990s (VanderWerf et al. 2001), and is placed between 1,500-2,000 mature individuals here, roughly equivalent to 2,200-3,000 individuals in total.
Population Trend: Decreasing

Habitat and Ecology [top]

Habitat and Ecology: The species is most abundant in mesic forest in valleys (VanderWerf et al. 2001), preferring mixed-species forest with a tall canopy and well-developed understorey, at 200-800 m (del Hoyo et al. 2006). The species is less common in drier forest (del Hoyo et al. 2006). It feeds on insects and other invertebrates (Scott et al. 1986).

Systems: Terrestrial

Threats [top]

Major Threat(s): Habitat loss to development has been extensive, with 56% of its former range zoned for agricultural or urban development (VanderWerf et al. 2001). Diseases such as avian pox and malaria, spread by mosquitoes, are a problem throughout its range, increasing mortality of adults by c.10-25%, and possibly preventing birds from nesting (E. VanderWerf in litt. 1999, VanderWerf et al. 2006). Malaria prevalence in the species has been recorded at 87%, with 36% of birds showing signs of avian pox (VanderWerf et al. 2006). High prevalence of mosquito-borne diseases and local declines in the species's population are associated with high rainfall (USFWS 2006, VanderWerf et al. 2006). Nest-predation by black rats Rattus rattus is the most serious current problem (VanderWerf et al. 1997, VanderWerf 1998, VanderWerf et al. 2001, VanderWerf 2009), leading to a male-biased sex ratio (VanderWerf et al. 2001). Fires are known to destroy key habitat and promote the spread of alien plants on O`ahu (USFWS 2006).

Conservation Actions [top]

Conservation Actions: Conservation Actions Underway
Rat control in 1996-2008 resulted in a 25% increase in survival of breeding females and a 100% increase in reproductive success, stabilising studied populations (VanderWerf and Smith 2002, VanderWerf 2009). Further rat control is currently taking place at other populations, but efficacy has been variable (VanderWerf et al. 2011b). Critical habitat has been designated on O`ahu (USFWS 2001). Captive breeding has been suggested (E. VanderWerf in litt. 1999). Recent research has shown that nesting height of Oahu Elepaios is increasing through evolution by selection from rat predation, which has lead to an overall increase in nest success in at least one population (VanderWerf in press).

Conservation Actions Proposed
Continue to monitor population trends and consider establishing a captive breeding population. Closely monitor the extent and quality of habitat. Conduct research into disease resistance (VanderWerf 2009). Implement further measures to control introduced rats (VanderWerf 2009). Protect forest from fires and development (USFWS 2006). Investigate whether nesting height is increasing in other parts of the island.
Citation: BirdLife International 2012. Chasiempis ibidis. The IUCN Red List of Threatened Species. Version 2014.3. <www.iucnredlist.org>. Downloaded on 01 February 2015.
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