Buteo solitarius 


Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Aves Accipitriformes Accipitridae

Scientific Name: Buteo solitarius
Species Authority: Peale, 1848
Common Name(s):
English Hawaiian Hawk
Spanish Busardo Hawaiano
Taxonomic Source(s): del Hoyo, J., Collar, N.J., Christie, D.A., Elliott, A. and Fishpool, L.D.C. 2014. HBW and BirdLife International Illustrated Checklist of the Birds of the World. Lynx Edicions BirdLife International.

Assessment Information [top]

Red List Category & Criteria: Near Threatened ver 3.1
Year Published: 2012
Date Assessed: 2012-05-01
Assessor(s): BirdLife International
Reviewer(s): Butchart, S. & Symes, A.
Contributor(s): Gorresen, M., Klavitter, J., Nelson, J. & Pratt, T.
Facilitator/Compiler(s): Benstead, P., Capper, D., Sharpe, C J, Stuart, T., Taylor, J.
This species is classified as Near Threatened because it has a very small population and a small range, for which there is currently no evidence of a decline. If the population was found to be declining, it would warrant uplisting to a higher threat category.

Previously published Red List assessments:
2008 Near Threatened (NT)
2004 Near Threatened (NT)
2000 Lower Risk/near threatened (LR/nt)
1994 Lower Risk/near threatened (LR/nt)
1988 Threatened (T)

Geographic Range [top]

Range Description: Buteo solitarius breeds on Hawai`i in the Hawaiian Islands (USA), with vagrants recorded on Maui, O'ahu and Kaua'i. The population is thought to be fairly stable (J. Nelson in litt. 2007), and estimates range from 1,457 (Klavitter et al. 2003) and 1,600 (1,120 adults) to 2,700 birds (Hall et al 1997, Griffin et al. 1998). The lack of information on historical numbers makes an assessment of this species difficult, and the underlying trend may be of gradual decline as nesting habitat disappears (J. Klavitter in litt. 1999). The rapid occupation of abandoned breeding territories suggests that the species may now be at or near the carrying capacity of remaining habitat (J. Nelson in litt. 2007).

Countries occurrence:
United States (Hawaiian Is.)
Continuing decline in area of occupancy (AOO): Unknown
Extreme fluctuations in area of occupancy (AOO): No
Estimated extent of occurrence (EOO) - km2: 7000
Continuing decline in extent of occurrence (EOO): Unknown
Extreme fluctuations in extent of occurrence (EOO): No
Continuing decline in number of locations: Unknown
Extreme fluctuations in the number of locations: No
Upper elevation limit (metres): 2700
Range Map: Click here to open the map viewer and explore range.

Population [top]

Population: Using a mean density of 0.004 birds/ha observed in 1993, and an estimate of 400,000 ha of suitable habitat on Hawai`i, an estimate of 1,600 birds, including 1,120 adults (560 pairs), was calculated by Hall et al. (1997). A similar estimate of 1,457 individuals was obtained from surveys in 1998-1999. The breeding population calculated by Hall et al. (1997) is rounded to 1,100 mature individuals.

Trend Justification:  The population is thought to be fairly stable and may be at or near the carrying capacity of remaining habitat (J. Nelson in litt. 2007).
Current Population Trend: Stable
Additional data:
Number of mature individuals: 1100 Continuing decline of mature individuals: Unknown
Extreme fluctuations: No Population severely fragmented: No
Continuing decline in subpopulations: Unknown
Extreme fluctuations in subpopulations: No All individuals in one subpopulation: No

Habitat and Ecology [top]

Habitat and Ecology: It occurs in a broad range of habitats up to 2,700 m, from lowland agricultural areas to all types of forest (Thiollay 1994, Hall et al 1997). However, most successful nesting is restricted to native `ohi`a trees Metrosideros polymorpha (which are slow growing and generally in decline) (J. Klavitter in litt. 1999). It benefits from some anthropogenic changes, for example, it feeds on introduced game-birds, passerines and rodents, and uses edge habitat around sugar-cane fields and orchards for hunting (Hall et al 1997, J. Klavitter in litt. 1999). The species reproduces at a slow rate, and there are observations that incubation lasts for 38 days, nestlings fledge after 59-63 days, and parents care for fledglings for an average of 30.2 weeks (Griffin et al. 1998). Parents feed nestlings with mostly mammalian and avian prey.

Systems: Terrestrial
Continuing decline in area, extent and/or quality of habitat: Unknown
Generation Length (years): 13.4
Movement patterns: Not a Migrant

Threats [top]

Major Threat(s): Continuing threats include forest clearance for agricultural and other developments, logging, the actions of introduced ungulates that degrade native forests and inhibit their regeneration, repeated nest disturbance, and perhaps road-kills (Scott et al. 1986, Thiollay 1994, J. Klavitter in litt. 1999). Nesting habitat in particular has been reduced, with recruitment of M. polymorpha restricted by competition from exotic plants in some areas (M. Gorresen in litt. 2007). The species is threatened by the conversion of land used for pasture and sugar-cane to eucalyptus plantations, and residential development in extensive areas of subdivided land, mainly in Puna District (T. Pratt in litt. 2007). It formerly suffered extensively from shooting and may come into conflict with future efforts to reintroduce the Critically Endangered Hawaiian Crow Corvus hawaiiensis, which it preys upon.

Conservation Actions [top]

Conservation Actions: Conservation Actions Underway
CITES Appendix II. Following surveys in 1998-1999, an island-wide survey for the species was carried out in 2007 (M. Gorresen in litt. 2007). A plan for the monitoring of the species's population is being developed (T. Pratt in litt. 2007). Ungulates are locally excluded from regenerating habitat (M. Gorresen in litt. 2007).

Conservation Actions Proposed
Protect habitat remnants from logging and clearance. Continue with long-term population monitoring. Continue to exclude introduced ungulates from regenerating habitat. Protect nests from disturbance.

Citation: BirdLife International. 2012. Buteo solitarius. The IUCN Red List of Threatened Species 2012: e.T22695929A40363410. . Downloaded on 27 November 2015.
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