Elepaio Chasiempis sandwichensis has been split into Hawaii Elepaio C. sandwichensis, Kauai Elepaio C. sclateri and Oahu Elepaio C. ibidis, following the American Ornithologists Union. Prior to this taxonomic change, C. sandwichensis was listed as Vulnerable under criterion B1a+b(i,ii,iii,iv,v) on the basis that the species had an Extent of Occurrence (EOO) estimated at 6,500 km2, in which its habitat is severely fragmented, its population was estimated to be declining at a rate of 25% over 10 years, and declines were observed, inferred or suspected in the EOO, Area of Occupancy, area, extent and/or quality of habitat and number of locations or sub-populations. Overall, these declines are driven by habitat loss for urban development and agriculture, unfavourable habitat management, the effects of introduced species, including pathogens, and catastrophic weather events.
This taxonomic change has prompted a review of the threat status of the relevant taxa, and it is proposed that C. sclateri and C. ibidis both be listed as Endangered. C. sclateri qualifies as Endangered under the B1 criteria because it has an EOO estimated at 420 km2 on Kaua`i, in which its habitat is considered to be severely fragmented and the species is provisionally suspected to be in decline based on past evidence and ongoing threats. A decline is suspected based on a reduction of c.50% in the species’s population following Hurricane Iniki in 1992 (Pratt 1994); however, this may have been temporary (Jacobi and Atkinson 1995).
C. ibidis qualifies as Endangered under the B1 criterion and potentially the C criterion. The species is eligible for Endangered status under the B1 criteria because it has an EOO estimated at 240 km2, in which its habitat is considered to be severely fragmented, and ongoing declines are provisionally suspected based on past evidence and ongoing threats. It potentially qualifies as Endangered under the C criterion on the basis that it has a population of c.1,800 mature individuals (USFWS 2006), which is provisionally suspected to be declining. However, to qualify the species must be shown to be declining at a rate of at least 20% over 12 years (estimate of two generations), or have sub-populations that number 250 individuals or less, or have one sub-population that contains at least 95% of all mature individuals. If the decline recorded by VanderWerf et al. (2001) of over 75% since 1975 is ongoing, the species may well meet the stipulated trend threshold. This could also qualify the species for threatened status under the A criterion, which stipulate that the population trend must be at least a 30% decline over 18 years (estimate of three generations) in the past, future or both. The ongoing threats of habitat loss for urban development and agriculture, fires and introduced species, including pathogens, seem to be particularly prevalent on O`ahu.
Comments are invited on these proposed listings under the IUCN criteria and detailed information is requested on the severity of threats and level of habitat fragmentation on both O`ahu and Kaua`i, and the estimated population trend and sub-population structure of both species.
Jacobi, J. D. and Atkinson, C. T. (1995) Hawaii’s endemic birds. Pp. 376-381 in LaRoe, E.T., ed. Our living resources: a report to the nation on the distribution, abundance, and health of US plants, animals, and ecosystems. Washington, D.C.: U.S. Department of the Interior, National Biological Service.
Pratt, H. D. (1994) Avifaunal change in the Hawaiian Islands, 1893-1993. Stud. Avian Biol. 15: 103-118.
U. S. Fish and Wildlife Service (2006) Revised Recovery Plan for Hawaiian Forest Birds. Honolulu, Hawaii: U.S. Fish and Wildlife Service.
VanderWerf, E. A., Rohrer, J. L., Smith, D. G. and Burt, M. D. (2001) Current distribution and abundance of the O’ahu ‘Elepaio. ‘Elepaio 61: 55, 57-61.