Data Zone
Justification of Red List category
This species has a restricted range where habitat degradation is ongoing, but it is not restricted to few locations. It is therefore assessed as Near Threatened.
Population justification
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 (Klavitter et al. 2003). However, a reanalysis of the 1998-1999 survey data using updated vegetation maps and methods to calculate population and density estimates suggested that the population actually numbered 3,239 (2,610-3,868) birds at this time (Gorreson et al. 2008). Using survey data from 2007, the population was estimated at 3,085 (2,496-3,680) birds, with no significant difference in densities between 1998 and 2007 (Gorreson et al. 2008). This is thought to be roughly equivalent to 1,700-2,500 mature individuals. It has been suggested that the species may now be at or near carrying capacity given rapid occupation of abandoned breeding territories (J. Nelson in litt. 2007).
Trend justification
Surveys suggest that the population size was consistently about 3,000 individuals between 1997 and 2007 (Gorresen et al. 2008) and the population is thought to have remained relatively stable in the time period 1980-2008. There has been no significant change to the population trend between 2008-2019 (USFWS 2020), and as such the trend is estimated to be stable.
Buteo solitarius breeds on Hawai`i in the Hawaiian Islands (USA), with vagrants recorded on Maui, O'ahu and Kaua'i.
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 ‘ōhi‘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.
Continuing threats include forest clearance for agricultural and other developments, 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). Rapid ʻŌhiʻa Death, a fungal pathogen infecting ‘ōhi‘a, is a severe threat to the integrity of native ‘ōhi‘a forests (USFWS 2020). However, Hawaiian hawks nest and hunt in a variety of native and nonnative habitats and may not be significantly affected by the ongoing threats to native habitat (USFWS 2020). It formerly suffered extensively from shooting and while this remains a threat, it is not thought to be having a significant impact given the population's stability over the past several decades (USFWS 2020). An increase in fire frequency due to alien plants and drought may reduce the amount of available habitat for nesting and perching, and this is likely to be exacerbated by climate change (USFWS 2020). Climate change is also increasing the risk of hurricanes and tropical storms (USFWS 2020).
Conservation Actions Underway
CITES Appendix II. Ungulates are locally excluded from regenerating habitat (M. Gorresen in litt. 2007). Invasive plant control and habitat restoration is ongoing within the range (USFWS 2020).
Text account compilers
Vine, J.
Contributors
Gorresen, M., Klavitter, J., Nelson, J. & Pratt, T.
Recommended citation
BirdLife International (2024) Species factsheet: Hawaiian Hawk Buteo solitarius. Downloaded from
https://datazone.birdlife.org/species/factsheet/hawaiian-hawk-buteo-solitarius on 23/11/2024.
Recommended citation for factsheets for more than one species: BirdLife International (2024) IUCN Red List for birds. Downloaded from
https://datazone.birdlife.org/species/search on 23/11/2024.