Birdfinding.info ⇒ The “Io” is generally common across much of the Big Island, more so on the eastern side. Sites where it can often be found include the kipukas along Saddle Road (especially on the Pu’u O’o Trail through Kipuka Ainahou), the restricted Pua Akala Tract in Hakalau Forest National Wildlife Refuge, the central part of Hawaii Volcanoes National Park, and the Pololu and Waipio Valley area.
Hawaiian Hawk
Buteo solitarius
Endemic to the Big Island of Hawaii, where it occurs islandwide in or over all habitat-types, at all elevations. More numerous in forests and partly wooded areas than in open grassland and sugarcane fields.
The total population has been stable in modern times, with estimates ranging from around 1,200 to 3,200—the variation in results apparently due more to statistical modeling than fluctuations in the population.
Fossil evidence suggests that it formerly inhabited Kauai and Molokai—which would likely imply other islands as well. There are many modern reports of sightings, some by experienced observers, but none with hard evidence (to rule out other species): four from Kauai, one from Oahu, three from Molokai, two from Lanai, and nine from Maui.
Identification
An unusually short, stout, broad-winged Buteo with highly variable plumage. Has a small, round, yellow cere on top of the base of the bill.
Often said to have a pale and a dark morph, but this dramatically understates its variation. In all plumages, the uppersides of the wings and tail are mostly dark-brown, but the rest of the plumage varies from whitish or pale-buffy to black.
Pale morph adults have variable amounts of spotting on the underparts, usually concentrated on the chest. Most have a dark-brown head and white throat.
Hawaiian Hawk, pale morph. (Hakalau Forest National Wildlife Refuge, Big Island, Hawaii; December 8, 2016.) © Laura Keene
Hawaiian Hawk, pale morph with evenly spotted underparts. (Saddle Road, Big Island, Hawaii; September 16, 2019.) © Teresa Connell
Hawaiian Hawk, pale morph showing dark head and white throat. (Pahoa, Big Island, Hawaii; February 21, 2019.) © Sherman Wing
Hawaiian Hawk, pale morph with dark head and dark vest. (Pua Akala Tract, Hakalau Forest National Wildlife Refuge, Big Island, Hawaii; July 21, 2016.) © Steven Freed
Hawaiian Hawk, pale morph with large dark-brown spots on the underparts. (Pua Akala Tract, Hakalau Forest National Wildlife Refuge, Big Island, Hawaii; November 2, 2016.) © Bob & Bettina Arrigoni
Hawaiian Hawk, pale morph with sparse, small streaks on white underparts. (Kalaoa, Big Island, Hawaii; September 16, 2018.) © Bradley Hacker
Hawaiian Hawk, pale morph. (Kea’au, Big Island, Hawaii; March 1, 2017.) © Carol Ortenzio
Hawaiian Hawk, pale morph with extensive rufous-brown spots on underparts. (Orchidland Estates, Big Island, Hawaii; October 23, 2017.) © Gret Dicey
Hawaiian Hawk, apparently intermediate between light and dark morph plumages. (Mauna Loa Road, Hawaii Volcanoes National Park, Big Island, Hawaii; March 23, 2011.) © Steve Heinl
Dark morph adults have underparts that vary from a bronzy medium-brown to blackish. On some individuals the underparts are variably mottled with paler spots.
Hawaiian Hawk, “typical” dark morph . (Hakalau Forest National Wildlife Refuge, Big Island, Hawaii; October 5, 2015.) © mnwild
Hawaiian Hawk, dark morph. (Akaka Falls State Park, Big Island, Hawaii; March 25, 2019.) © Rich Brown
Hawaiian Hawk, dark morph with blackish-brown plumage overall. (Pu’u O’o Trail, Kipuka Ainahou, Big Island, Hawaii; April 5, 2017.) © Curt Hofer
Hawaiian Hawk, dark morph with blackish plumage. (Kilauea Iki, Hawaii Volcanoes National Park, Big Island, Hawaii; March 8, 2018.) © Grace Nelson
Hawaiian Hawk, dark morph with reddish-brown plumage, mottled with paler spots. (Pu’u O’o Trail, Kipuka Ainahou, Big Island, Hawaii; March 2, 2018.) © Bill Bryneteson
Hawaiian Hawk, dark morph with evenly blackish plumage. (Saddle Road, Big Island, Hawaii; October 25, 2019.) © John Sullivan
Hawaiian Hawk, dark morph with medium-brown underparts. (Keanakolu Road, Big Island, Hawaii; October 21, 2017.) © Sharif Uddin
Hawaiian Hawk, dark morph mottled with paler spots. (Kapoho Bay, Big Island, Hawaii; February 18, 2017.) © Steve Compton
Hawaiian Hawk, dark morph with blackish-brown plumage overall. (Waipio Valley, Big Island, Hawaii; November 17, 2019.) © Ann Vaughan
Hawaiian Hawk, dark morph on nest. (Kalopa State Park, Big Island, Hawaii; June 25, 2009.) © Michael Walther
Hawaiian Hawk, dark morph drying its wings. (Pua Akala Tract, Hakalau Forest National Wildlife Refuge, Big Island, Hawaii; November 28, 2015.) © Alan Van Norman
Pale morph immatures have whitish or pale-buffy head and underparts, often with a dark mask, eyeline, or shading on the face.
Hawaiian Hawk, pale morph immature showing patchy buffy and whitish head and underparts with dark mask. (Big Island, Hawaii; March 28, 2015.) © Lisa Kinsey
Hawaiian Hawk, pale morph immature. (Manuka State Park, Big Island, Hawaii; January 24, 2017.) © Don Coons
Hawaiian Hawk, pale morph immature. (Kipuka Puaulu, Hawaii Volcanoes National Park, Big Island, Hawaii; January 11, 2019.) © Bob Lockett
Hawaiian Hawk, pale morph immature showing entirely unmarked underparts. (Manuka State Park, Big Island, Hawaii; January 24, 2017.) © Don Coons
Hawaiian Hawk, pale morph immature showing contrasting dark upperparts and pale-buffy head and underparts with dark mask. (Pahala, Big Island, Hawaii; January 24, 2020.) © Douglas Long
Hawaiian Hawk, pale morph immature showing contrasting dark upperparts and pale-buffy head and underparts with dark mask. (Big Island, Hawaii; March 28, 2015.) © Lisa Kinsey
Hawaiian Hawk, pale morph immature. (Kilauea Iki, Hawaii Volcanoes National Park, Big Island, Hawaii; March 22, 2017.) © Karen Povey
Hawaiian Hawk, pale morph immature. (Keanakolu Road, Big Island, Hawaii; August 13, 2017.) © Milton Vine
Hawaiian Hawk, pale morph immature. (Pu’u O’o Trail, Kipuka Ainahou, Big Island, Hawaii; April 21, 2019.) © Sherman Wing
Hawaiian Hawk, pale morph. (Volcano, Big Island, Hawaii; April 30, 2019.) © Lizabeth Southworth
Hawaiian Hawk, pale morph. (Kailua-Kona, Big Island, Hawaii; October 24, 2019.) © Anthony Gliozzo
Hawaiian Hawk, pale morph. (Pu’u O’o Trail, Kipuka Ainahou, Big Island, Hawaii; November 22, 2019.) © Trina Anderson
Hawaiian Hawk, pale morph. (Hawaii Volcanoes National Park, Big Island, Hawaii; September 22, 2019.) © Sarah Newton-Scott
Hawaiian Hawk, pale morph immature. (Pololu Valley, Big Island, Hawaii; September 27, 2018.) © Alex Wang
Hawaiian Hawk, pale morph. (Pu’u La’au, Big Island, Hawaii; December 27, 2018.) © Jeff Stacey
Hawaiian Hawk, pale morph. (Keanakolu Road, Big Island, Hawaii; August 30, 2017.) © Alan Schmierer
Hawaiian Hawk, pale morph. (Pua Akala Tract, Hakalau Forest National Wildlife Refuge, Big Island, Hawaii; September 23, 2018.) © Kathryn Hart
Hawaiian Hawk, pale morph. (Kilauea Lodge, Volcano, Big Island, Hawaii; July 9, 2017.) © Doug Gochfield
Hawaiian Hawk, “typical” dark morph showing underwing pattern. (Hakalau Forest National Wildlife Refuge, Big Island, Hawaii; October 5, 2015.) © mnwild
Hawaiian Hawk, dark morph. (Waldrin’s Ledge Trail, Hawaii Volcanoes National Park, Big Island, Hawaii; April 9, 2016.) © Allan Robbins
Hawaiian Hawk, dark morph. (Pua Akala Tract, Hakalau Forest National Wildlife Refuge, Big Island, Hawaii; December 4, 2017.) © Loch Kilpatrick
Hawaiian Hawk, dark morph. (Hakalau Forest National Wildlife Refuge, Big Island, Hawaii; March 12, 2017.) © Max Rabinowitz
Hawaiian Hawk, dark morph. (Akaka Falls State Park, Big Island, Hawaii; March 25, 2019.) © Rich Brown
Hawaiian Hawk, dark morph. (Pua Akala Tract, Hakalau Forest National Wildlife Refuge, Big Island, Hawaii; August 5, 2017.) © Thanasis Tsafonis
Hawaiian Hawk, dark morph. (Pua Akala Tract, Hakalau Forest National Wildlife Refuge, Big Island, Hawaii; July 2, 2016.) © Jacob Drucker
Hawaiian Hawk, dark morph. (Volcano House, Hawaii Volcanoes National Park, Big Island, Hawaii; December 10, 2019.) © William Richards
Voice. Typical call is a shrill “eee-oh,” the basis of its local name: Io.
Notes
Monotypic species.
IUCN Red List Status: Near Threatened.
References
BirdLife International. 2016. Buteo solitarius. The IUCN Red List of Threatened Species 2016: e.T22695929A93534506. https://dx.doi.org/10.2305/IUCN.UK.2016-3.RLTS.T22695929A93534506.en. (Accessed August 15, 2020.)
eBird. 2020. eBird: An online database of bird distribution and abundance. Cornell Lab of Ornithology, Ithaca, N.Y. http://www.ebird.org. (Accessed August 15, 2020.)
Ferguson-Lees, J., and D.A. Christie. 2001. Raptors of the World. Houghton-Mifflin, Boston.
Pratt, H.D., P.L. Bruner, and D.G. Berrett. 1987. A Field Guide to the Birds of Hawaii and the Tropical Pacific. Princeton University Press.
Pratt, H.D. 1993. Enjoying Birds in Hawaii: A Birdfinding Guide to the Fiftieth State (Second Edition). Mutual Publishing, Honolulu, Hawaii.
Pyle, R.L., and P. Pyle. 2017. The Birds of the Hawaiian Islands: Occurrence, History, Distribution, and Status. Version 2 (January 1, 2017). http://hbs.bishopmuseum.org/birds/rlp-monograph/. B.P. Bishop Museum, Honolulu, Hawaii.