The Hawaiian Hawk or 'Io, Buteo solitarius, is a raptor of the Buteo genus endemic to Hawai'i. Buteos tend to be easily recognized by their bulky bodies relative to their overall length and wingspan. The 'Io is the only hawk that is native to Hawaii, where they are only known to breed on the Big Island in stands of native `ohi'a lehua trees. The species is protected as Endangered in the United States. However, the IUCN classifies the species as Near Threatened.
The Hawaiian Hawk measures approximately 40 to 46 centimeters (16 to 18 inches) in length. The female is larger than the male. 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 juveniles.
Common threats for the hawk are illegal shootings, the degradation of their native forest habitat, poisoning, vehicle collisions, starvation, and predation from other animals.
This solitary hawk remains in and defends its territories year round. They nest from March through September, and usually lay only one egg but sometimes they could lay up to three in their clutch. 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. Fifty to seventy percent of the nest successfully fledge young.
The 'Io usually hunts from a stationary position, but can also dive on prey from the air. It feeds on rats, small birds, stream animals, crickets, praying mantises, millipedes, centipedes, and occasionally the worm. It will also feed on the Hawaiian Crow, another one of Hawaii's endangered 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 breeding season. 'Io are strong fliers.
The Hawaiian hawk was a royal symbol in Hawaiian legend, and it is sometimes called "'Iolani,"? or "Exalted Hawk"?, which was the name of Kamehameha IV and the ?Iolani Palace.