- State Listed as Endangered
- State Recognized as Endemic
- NatureServe Heritage Rank G2—Imperiled
- IUCN Red List Ranking—Near Threatened
- Hawaiian Hawk Recovery Plan—USFWS 1984
The ‘io, or Hawaiian hawk, is the only broad-winged hawk (Family: Accipitridae) in Hawai‘i. ‘Io are considered ‘aumākua, or family gods, by Native Hawaiians. Similar to many birds of prey, females are larger than males, and often weigh approximately 25 percent more than males. Also similar to many Buteos, two color morphs, light and dark, occur in ‘io populations. Prior to the arrival of Polynesians, ‘io may have exclusively preyed on birds, including now extinct flightless ibis, and rails. Its diet now includes non-native insects, birds and rodents, as well as native insects and birds. ‘Io form monogamous long-term pair-bonds and defend territories year-round. Nest construction is lengthy, beginning up to two months before the first egg is laid, and continuing into the nestling period. Egg-laying generally occurs from March to June, and fledging (when young birds begin flying) from July to September. Both sexes contribute to nest-building. Egg produced is nearly always one, although historically two and three eggs were reported. Both sexes incubate, although females perform most of the brooding of nestlings; males provide most of the food to chicks and female. Both adults feed fledglings, which are dependent on adults for up to nine months.
Occurs throughout the island of Hawai‘i from 300 to 2,600 meters (1,000 to 8,530 feet). Based on fossil evidence, they once occurred on Kaua‘i, Moloka‘i, and O‘ahu.
Lowland non-native forests, urban areas, agricultural lands, pasturelands, and high-elevation native forests. Most nesting occurs in native ‘ōhi‘a trees, although also occurs in non-native trees, including eucalyptus, ironwood, mango, coconut palm, and macadamia. In winter, they have been reported in subalpine māmane-naio forest, suggesting some seasonal movements.
- Habitat loss and degradation. Habitat is negatively affected by urbanization, land conversion to unsuitable foraging habitat (e.g., pasture and cane fields to eucalyptus forest), increase in fire frequency that may eliminate nesting and perching habitat, and invasion of understory plants which can conceal prey and reduce foraging success. However, the species was proposed to be federally delisted in 2008, and again in 2014, because it was determined that the species is resilient enough to maintain itself in a variety of non-native and native habitat types.
- Disease. ‘Io does not appear to be susceptible to the avian malaria and avian pox that have devastated other Hawaiian endemic forest birds. However, West Nile virus could affect the species if the disease reaches Hawai‘i.
For more information and references visit the DLNR State Wildlife Action factsheets. DOFAWʻs species pages and State Wildlife Action Plan fact sheets are provided for general information and are not meant to be a citable, original source of data. If you are a student, researcher, or writer looking for a citable source, please explore the references below or find other original data sources, rather than citing these webpages. The references below were provided by the authors of the State Wildlife Action Plan fact sheets at the time of drafting:
- Clarkson KE, Laniawe LP. 2000. Hawaiian hawk (Buteo solitarius). In The Birds of North America, No. 523 (Poole A, Gill F, editors). Philadelphia, (PA): The Academy of Natural Sciences; and Washington DC: The American Ornithologists’ Union.
- Hawai‘i Natural Heritage Program [Hawai‘i Biodiversity and Mapping Program]. 2004. Natural diversity database. University of Hawai‘i, Center for Conservation Research and Training. Honolulu, HI.
- IUCN Red List of Threatened Species. 2015. Version 2014.3. www.iucnredlist.org. (Accessed May 2015).
- NatureServe. 2015. NatureServe Explorer: An online encyclopedia of life [web application]. Version 7.1. NatureServe, Arlington, Virginia. Available at: https://explorer.natureserve.org. (Accessed May 2015).
- Scott JM, Mountainspring S, Ramsey FL, Kepler CB. 1986. Forest bird communities of the Hawaiian islands: their dynamics, ecology and conservation. Lawrence, (KS): Cooper Ornithological Society.
- U.S. Fish and Wildlife Service. 1984. Hawaiian Hawk Recovery Plan. Portland, Oregon.
- U.S. Fish and Wildlife Service. 2008. Endangered and threatened wildlife and plants; withdrawal of proposed reclassification of the Hawaiian hawk or io (Buteo solitarius) from endangered to threatened; proposed rule to remove the Hawaiian hawk from the federal list of endangered and threatened wildlife. Federal Register 73:45680–45689.
- U.S. Fish and Wildlife Service. 2008. Draft Post-delisting Monitoring Plan for the Hawaiian Hawk, or Io (Buteo solitarius). Endangered Species Division, Pacific Island Fish and Wildlife Office, Honolulu, HI.