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Hawaiian Hawk
Buteo solitarius

Status: Near Threatened

Population Trend: Stable.

Other Names: Hawaiian Buzzard, I'o.

Buteo solitarius
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Distribution: Oceanian. Endemic to Hawai'i (Island of Hawai'i; vagrants on Oahu, Kauai, and Maui).

Subspecies: Monotypic.

Taxonomy: Molecular genetics studies indicate that this insular species forms a clade with B. galapagoensis, B. swainsoni, and B. brachyurus (Fleischer and McIntosh 2001, Riesing et al. 2003).

Movements: Irruptive or local migrant, with juveniles dispersing from breeding areas (Bildstein 2006).

Habitat and Habits: Griffin (1985) and Hall et al. (1997) found this species in a wide variety of native and exotic habitats. Klavitter (200) noted that the highest densities of Hawaiian Hawks occur in areas of mature native forest with large portions of human-created edge habitat and extensive areas with alien grasses.

Food and Feeding Behavior: Griffin (1985) reported that the Hawaiian Hawk utlizes a wide variety of introduced and native prey items, including 13 species of birds, five species of mammals, and one insect species. Composition of the diet varies between the sexes and between different habitat types.

Breeding: The following details are taken from Griffin (1985): Eggs are laid from March to June, but pairs do not attempt breeding in some years. Nests are bulky structures made of sticks and placed in a wide bariety of trees. Both sexes participate in nest building and incubation, but only the female broods the young, with the male providing most of the food at nests through the first four weeks of the nesting period. Griffin (opc it.) found only a single egg in 30 nests, despite earlier reports of clutch sizes of two or three eggs. The egg is pale bluish- or greenish-white when laid. The incubation period is about 38 days, and the nesting period lasts from 59 to 63 days. Adults delivered prey to juveniles for 25-37 weeks after fledging.

Conservation: The population is considered to be stable (Hall et al. 1997, Klavitter 2000). Former declines were caused mainly by shooting and other forms of direct persecution, and this species may also have suffered from diseases, including avian pox. Klavitter (op cit.) recommended that the species could be downlisted and acknowledged that it might be completely delisted. Considered to be Near Threatened by BirdLife International.

Population Estimates: Griffin (1985) estimated the population in 1983 at 1,400 to 2,500 birds, based on the optimistic assumption that density of the species was the same throughout the island as in his study area. He later revised his estimate to 900 breeding pairs and a total population of 2,700 individuals (Griffin 1989). Based on a point count survey in 1993, Morrison et al. (1994) and Hall et al. (1997) placed the population at 1,600 individuals, including 560 breeding pairs. Klavitter (2000) estimated the total population at 1,457 (SE = 176.3) individuals, based on surveys conducted in 1998 and 1999, and also calculated the total population in 1993 at 1,017 individuals.

Important References: 
Baskett, T.E., and C.R. Griffin. 1981. Biology of the endangered Hawaiian
  Hawk; ecology, life history and environmental pollution problems. U.S. Fish
  and Wildlife Service, Washington, D.C. 220 pp.
Clarkson, K., and L. Laniawe. 2000. Hawaiian Hawk (Buteo solitarius). Pp.
  1-16 in A. Poole and F. Gills (eds.), The Birds of North
  America no. 523. The Birds of North America, Inc., Philadelphia, PA.
Fleischer, R.C., and C.E. McIntosh. 2001. Molecular systematics and
  biogeography of Hawaiaan avifauna. Studies in Avian Biology 22:51-60.
Griffin, C.R. 1985. Biology of the Hawaiian Hawk (Buteo solitarius). Ph.D.
  dissertation, University of Missouri, Columbia, MO.
Griffin, C.R. 1989. Raptors in the Hawaiian Islands. Pp. 155-160 in B.
  Giron Pendleton, C.E. Ruibal, D.L. Krahe, K. Steenhof, M.N. Kochert, and
  M.N. LeFranc, Jr.(eds.), Proceedings of the Western Raptor Management
  Symposium and Workshop. National Wildlife Federation, Washington, D.C.
Griffin, C.R., P.W. Paton, and T.S. Baskett. 1998. Breeding ecology and
  behavior of the Hawaiian Hawk. Condor 100:654-662.
Hall, L.S., M.L. Morrison, and P.H. Bloom. 1997. Population status of the
  endangered Hawaiian Hawk. Journal of Raptor Research 31:11-15.
Klavitter, J.L. 2009. The ecology and conservation of Hawaiian raptors.
  Pp. 293-311 in T.K. Pratt, C.T. Atkinson, P. Banko, J.D. Jacobi, and B.L.
  Woodworth (eds.), Conservation biology of Hawaiian forest birds:
  implications for island avifauna. Yale University Press, New Haven, CT.
Klavitter, J.L., J.M. Marzluff, and M.S. Vekasy. 2003. Abundance and
  demography of the Hawaiian Hawk: is delisting warranted? Journal of Wildlife
  Management 67:165-176.
Olson, S.L., and H.F. James. 1997. Prehistoric status and distribution of
  the Hawaiian Hawk (Buteo solitarius), with the first fossil record from
  Kauai. Bishop Museum Occasional Papers 48:65-69.
U.S. Fish and Wildlife Service. 1984. Hawaiian Hawk recovery plan. U.S.
  Fish and Wildlife Service, Portland, OR.
White, C.M. 1994. Hawaiian Hawk. P. 184 in del Hoyo, J., A. Elliott, and
  J. Sargatal (eds). Handbook of birds of the world. Vol. 2. New World
  vultures to guineafowl. Lynx Edicions, Barcelona, Spain.

Sites of Interest:
Hawaiian Hawk photos.

Last modified: 11/8/2012

Recommended Citation: Global Raptor Information Network. 2017. Species account: Hawaiian Hawk Buteo solitarius. Downloaded from http://www.globalraptors.org on 25 Feb. 2017

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