It is now restricted to an area of 47 square kilometers (18 sq mi) in the Koʻolau and Waiʻanae ranges, where a fragmented population of 1,200-1,400 birds occurs. It is listed as endangered; avian malaria and fowlpox are widespread in the population and although it appears to have weathered the worst of it, it is threatened by a combination of these diseases and predation of nestlings, eggs and adult females by rats. In areas where rats are controlled, survival and nest success are higher. Recently completed surveys of populations in the Koʻolau range have unexpectedly revealed that the population has largely remained stable since surveys conducted in the 1990s. However, only about 20 individuals are left on the windward side of the Koʻolau range, with some valleys containing only a single ʻelepaio. Without intervention, this population faces extirpation in the near future due to small population phenomena. This species looks very similar to the Hawaiʻi ʻelepaio, but the white underside extends to the flanks and further up the breast, and the upperside - especially the head - is more rust-colored.
- BirdLife International (2008). "Chasiempis ibidis". IUCN Red List of Threatened Species. Version 2009.2. International Union for Conservation of Nature. Retrieved 2 July 2012.
- Conant, S. (1977): The breeding biology of the Oahu ʻElepaio. Wilson Bull. 89(2): 193-210. DjVu fulltext PDF fulltext
- VanderWerf, Eric A.; Rohrer, Joby L.; Smith, David G. & Burt, Matthew D. (2001): Current distribution and abundance of the Oʻahu ʻElepaio. Wilson Bull. 113(1): 10-16. DOI:10.1676/0043-5643(2001)113[0010:CDAAOT]2.0.CO;2 HTML abstract
- VanderWerf, Eric A.; Burt, Matthew D.; Rohrer, Joby L. & Mosher, Stephen M. (2006): Distribution and prevalence of mosquito-borne diseases in Oʻahu ʻElepaio [English with Spanish abstract]. Condor 108(4): 770-777. DOI:10.1650/0010-5422(2006)108[770:DAPOMD]2.0.CO;2 HTML abstract
- Species Factsheet - BirdLife International