ʻIo

Buteo solitarius / Hawaiian Hawk
Hawaiian Hawk

This graceful bird of prey measures 16 to 18 inches in length, the female being larger. Two color phases exist: a dark phase (dark brown head, breast, and underwings), and a light color phase (dark head, light breast and light underwings). Feet and legs are yellowish in adults and greenish in immatures.

The ‘io is endemic to Hawai‘i and was a symbol of royalty in Hawaiian legend. The ‘io is also the only hawk today native to Hawai‘i. They only breed on the Big Island but have been occasionally seen on Maui, O‘ahu, and Kaua‘i. Fossil records indicate that this hawk may also been established on Moloka‘i and Kaua‘i. They depend on native forest for nesting, but are able to use a broad range of habitats for foraging, including papaya and macadamia nut orchards, as well as forests dominated by native and introduced vegetation, from sea level to 6,500 feet elevation.

This mostly solitary hawk remains in and defends its territories year round. They nest from March through September, and usually lay only one egg. The female does the majority of sitting during the 38 days of incubation, while the male does the majority of the hunting. After the egg is hatched, the female only allows the male to visit when delivering food to the nest. The chick fledges at seven or eight weeks.

 

The ‘io usually hunts from a stationary position, but can also dive on prey from the air. It feeds on rodents, insects, small birds, and some game birds. They are opportunistic predators and are versatile in their feeding habits. They have a shrill and high-pitched call much like their Hawaiian name: "eeeh-oh." They are known to be very noisy during the breading season. ‘Io are strong fliers.

Conversion of native forest to residential, large-scale agriculture, exotic forestry, and to business and industrial areas have been and will continue to have the greatest negative impact on this species. Hawaiian hawks can be seen souring over or foraging in these changed areas but they typically do not nest in them. These areas may also be a source of high mortality, especially for young birds. Shooting, vehicle collisions; poisoning; starvation; and predation by dogs, cats, and mongoose are documented sources of mortality. 

Facts About ʻIo

Although the Hawaiian Archipelago was once home to an eagle, a harrier, and a hawk, only the Hawaiian Hawk, or 'Io, managed to survive the human colonization of the Hawaiian Islands. Today, the Hawaiian Hawk is listed as a federally endangered species, threatened by illegal shooting, harassment of nesting birds, and degradation of native forest nesting habitat.