The Hawaiian common moorhen (Gallinula chloropus sandvicensis) was common on the main Hawaiian islands except Lana`I and Kaho`olawe in the late 19th century. By the late 1940s it was described as "precarious," especially on Oahu, Molokai, and Maui . The Molakai population was extirpated after the 1940s, reintroduced in 1982, but did not persist and is currently absent from the island . The spread of aquaculture on Oahu and Kauai in the late 1970's and the 1980's likely benefited the species. Aquaculture projects currently support some of the highest concentrations of moorhens in the state .
The population was estimated at no more than 57 in the 1950s and 1960s  and about 750 in 1985 (500 on Kauai, 250 on Oahu, and a small number on Molokai) , but this may be underestimate . The accuracy of these estimates is questionable because the species is very secretive and not conducive to standard waterbird census methods. Waterbird counts from 1977 to 2003 indicate a increasing population trend, though absolute population numbers can not be drawn from them .
 U.S. Fish and Wildlife Service. 2005. Draft Revised Recovery Plan for Hawaiian Waterbirds, Second Draft of Second Revision. U.S. Fish and Wildlife Service, Portland, Oregon. 155 pp.
 Engilis, A., Jr., and T. K. Pratt. 1993. Status and population trends of Hawaii's native waterbirds, 1977-1987. Wilson Bull. 105:142-158
 U.S. Fish and Wildlife Service. 1985. Recovery Plan for the Hawaiian Waterbirds. U.S. Fish and Wildlife Service, Portland, OR.