BC Conservation Data Centre: Conservation Status Report
Buteo swainsoni
Swainson's Hawk
| Scientific Name: | Buteo swainsoni |
|---|---|
| English Name: | Swainson's Hawk |
| Provincial Status Summary | |
| Status: | S2B |
| Date Status Assigned: | June 30, 1998 |
| Date Last Reviewed: | March 25, 2022 |
| Reasons: | Surveys have found few breeding pairs in the province concentrated in a few areas of the Thompson-Okanagan, some of which are under development presures. |
| Range | |
| Range Extent: | FG = 20,000-2,500,000 square km |
| Range Extent Estimate (km2): | 259,000 square km |
| Range Extent Comments: | Breeds mainly in the Thompson-Okanagan Plateau; from Princeton and Anarchist Mountain north to the northern Okanagan and Thompson River valleys; also locally in the Bulkley Basin (Campbell et al. 1990,Fraser 2015). The majority of records are from the southern interior where breeding is concentrated in the Nicola the north vast Okanagan, and the plateau east of Osoyoos (Campbell et al. 1990; Cooper 1998, Fraser 2015). Atlas-period breeding of Swainson's Hawks is almost entirely restricted to the Southern Interior Ecoprovince. Campbell et al. (1990) also documented a small isolated breeding population in the Bulkley Valley. BC Breeding Bird Atlasers found the species in the Bulkley Valley but failed to confirm breeding there. However, birds continue to be seen there and records of juvenile birds with an adult (e.g. https://ebird.org/checklist/S59836838) suggests the species still breeds in the area. Swainson's Hawks appear to have expanded their range into the Boreal Plains and Sub-Boreal Interior ecoprovinces since The Birds of British Columbia was published in 1990, but in very small numbers (Fraser 2015). While there is only possible breeding evidence during the Breeding Bird Atlas in these new areas, the species was documented breeding in the Peace River lowlands in the early 2000's, and likely bred in the Boreal Plains Ecoprovince during the period 2008-2012 (Phinney pers comm.). Probable breeding in one square in each of the Coast Mountains, Central Interior and Sub-Boreal Interior suggests the species may be a very rare breeder over a larger part of the province than was previously believed. Not known to breed in the east Kootenay grasslands at present (Cooper 1998; F. Beebe, pers. comm.). |
| Area of Occupancy (km2): | E = 26-125 |
| Area of Occupancy Estimate (km2): | at least 10, likely significantly more |
| Area of Occupancy Comments: | While the occurrences in the North Okanagan and Thompson-Nicola are somewhat adequately documented, the others in the province (the Bulkley Valley, the northeast and the far north) are poorly documented and may be unpredictably occuppied and are difficult to estimate at this time. BC CDC has 6 EOs on file, the BC Breeding Bird atlas documented confirmed breeding in 14 10x10 km atlas squares which may represent more than one grid cell/square. |
| Occurrences & Population | |
| Number of Occurrences: | C = 21 - 80 |
| Comments: | Nest records exist from Princeton, Okanagan Landing, Vernon, Goose Lake Range, and the plateau east of Osoyoos (Cannings, et al. 1987). Localized breeding also occurs near Hazelton (Campbell et al. 1990). Cooper found three active nests near Vernon and two nests plus several other pairs in the Douglas Lake area (Cooper 1998). Islolated breeding records in the Peace River area, and probable breeding records in scattered areas in other parts of the province were documented during the BC Breeding Bird Atlas period (Fraser 2015). |
| Number of Occurrences with Good Viability / Ecological Integrity: | Rank Factor not assessed |
| Number of Occurrences Appropriately Protected & Managed: | A = None |
| Comments: | Most breeding habitat within its provincial range is privately owned, making protection difficult. Some nests are on Crown lands. |
| Population Size: | AC = 1 - 1,000 individuals |
| Comments: | Cooper (1998) estimated 50 pairs in the Douglas Plateau area and 25 pairs in the north Okanagan. Since the 1920s, there have been no large aggregations of this species reported in the province. Campbell et al 1990 reported as many as 15 birds can be seen in autumn flocks (Campbell et al. 1990), but these numbers have not been seen recently. Largest flock reported on eBird from BC is a group of 14 seen in June 2018 in the Cariboo (https://ebird.org/checklist/S46545837). |
| Threats (to population, occurrences, or area affected) | |
| Degree of Threat: | Rank Factor not assessed |
| Comments: | Shooting and pesticide use in the winter range continues to threaten population numbers (Woodbridge et al. 1995). In British Columbia, loss of grassland habitat to urban sprawl and agriculture, as well as current pesticide control which reduce prey abundance have been attributed to population declines (Cannings et al. 1987). Forest encroachment into grasslands (a result of fire suppression) is also a threat. |
| Trend (in population, range, area occupied, and/or condition of occurrences) | |
| Short-Term Trend: | F = Decline of 10-30% |
| Comments: | Current populations are low compared to historical accounts. Recent trends are unknown, but populations are likely declining. Continued shooting and pesticide poisoning in Argentina suggest numbers could decline here, but we do not know if birds from British Columbia winter in Argentina (Woodbridge et al. 1995). Declines are likely continuing, despite some apparent modest range expansion. |
| Long-Term Trend: | C = Decline of 70-80% |
| Comments: | Prior to the 1920's very large flocks were seen in the fall (Campbell et al. 1990) |
| Other Factors | |
| Intrinsic Vulnerability: | Rank Factor not assessed |
| Environmental Specificity: | Rank Factor not assessed |
| Other Rank Considerations: | |
| Information Gaps | |
| Research Needs: | |
| Inventory Needs: | Thorough surveys for nesting Swainson's Hawks should be conducted in the north Okanagan Valley, Anarchist Mountain, Bulkley Valley and Douglas Plateau areas using standarized methods (Resour. Inventory Comm. 1997 #11) to determine populations in the two core breeding areas for the province. These data are needed in order to assess the regional and provincial conservation priorities that should be placed on this species. Surveying for nests by helicopter during the incubation period is likely the most efficient technique, particularly in the Douglas Plateau area. Public information programs in the more developed parts of the range (e.g., the Okanagan) could also improve survey effectiveness. Encouraging birders to report birds in other parts of the province or post them on eBird, especially breeding records will be important to document the apparent range expansion (Fraser 2015) |
| Stewardship | |
| Protection: | |
| Management: | Large tracts of open grassland or rangeland should be conserved in areas of high population concentration. Education programs should be developed for local landowners explaining the importance of conserving this species and its useful role in controlling insect and rodent pests. Known nesting areas should be checked annually to provide population trend data. Tree bluffs or shelter belts should not be destroyed or cut throughout its breeding range. Pesticide use should be managed to minimize negative impacts on Swainson's Hawk prey. Investigate the potential for enhancement of existing nesting habitat and the creation of new nesting habitat. Assess the impact of forest encroachment in grasslands on Swainson's Hawk habitat (Cooper 1998). |
| Version | |
| Author: | S. Cannings and L. Ramsay updated by David F Fraser (2022) |
| Date: | March 17, 2020 |
| References | |
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Bechard et al. 2010. Swainson's Hawk (Buteo swainsoni), version 2.0 in The Birds of North America (A.F. Poole, ed.). Cornell Lab of Ornithology, Ithaca, NY, USA.
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Beebe, F.L. 1974. Field studies of the Falconiformes of British Columbia: vultures, hawks, falcons, eagles. B.C. Prov. Mus. Occas. Pap. No. 17, Victoria, 163pp.
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Campbell, R.W., N.K. Dawe, I. McTaggart-Cowan, et al. 1990b. The Birds of British Columbia Vol. 2: Nonpasserines: Diurnal Birds of Prey through Woodpeckers. Royal British Columbia Museum, Victoria, BC.
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Cannings, R.A., R.J. Cannings, and S.G. Cannings. 1987. Birds of the Okanagan Valley, B.C. Royal B.C. Mus., Victoria, BC. 420pp.
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Cannings, R.J. 1998. The Birds of British Columbia - a taxonomic catalogue. B.C. Minist. Environ., Lands and Parks, Wildl. Branch, Victoria, Wildl. Bull. B-86. 266pp.
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Cooper, J.M. 1998. An Inventory Report on the Status of Diurnal Raptors (Ferruginous Hawk, Swainson's Hawk, Prairie Falcon, Peregrine Falcon) at Risk in the Southern Grasslands of British Columbia. B.C. Minist. Environ., Lands and Parks, Wildl. Branch. Working Rep. WR-92. 24pp.
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England, A.S., M.J. Bechard, and C.S. Houston. 1997. Swainson's Hawk (Buteo swainsoni). in A. Poole, and F. Gill, eds. The Birds of North America, No. 265. Acad. Nat. Sci., Philadelphia, PA, and Am. Ornithol. Union, Washington, DC.
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Fraser, D.F. 2015. Swainson's Hawk in Davidson, P.J.A., R.J. Cannings, A.R. Couturier, D. Lepage, and C.M. Di Corrado (eds.). The Atlas of the Breeding Birds of British Columbia, 2008-2012. Bird Studies Canada. Delta, B.C.
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Gilmer, D. S., and R. E. Stewart. 1984. Swainson's hawk nesting ecology in North Dakota. Condor 86:12-18.
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Resource Inventory Committee. 1997e. Standardized Inventory Methodologies for Components of British Columbia's Biodiversity: Raptors, version 1.1. Prepared for the Resour. Inventory Comm., B.C. Minist. Environ., Lands and Parks, Victoria, BC. 56pp.
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Schmutz, J.K. 1987. The effect of agriculture on Ferruginous and Swainson's Hawks. J. Range Manage. 40:438-440.
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Woodbridge, B., K.K. Finley, and S.T. Seager. 1995. An investigation of the Swainson's Hawk in Argentina. J. Raptor Res. 29:202-204.
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Please visit the website Conservation Status Ranks for information on how the CDC determines conservation status ranks. For global conservation status reports and ranks, please visit the NatureServe website http://www.natureserve.org/.
Suggested Citation:
B.C. Conservation Data Centre. 2020. Conservation Status Report: Buteo swainsoni. B.C. Minist. of Environment. Available: https://a100.gov.bc.ca/pub/eswp/ (accessed Mar 13, 2025).