Basic Information
Common Name: Swainson's Hawk
Scientific Name: Buteo swainsoni
Species Code:
Management Category: VG (species not specifically managed for, but may benefit from vegetation management for VF species)
Occurrence Map
Table of Occurrences
File name Lead Author Year Type
County of San Diego MSCP Monitoring Summary Report January 1998 - June 2007 County of San Diego 2007 report
Ramona Grasslands: Historical Perspective Bittner, David 2008 report

Current Distribution Rangewide

Distribution occurs from western North America throughout the Great Plains of the U.S., into Central America, migrating as far south as Argentina [1].

Known Populations in San Diego County

A rare migrant of San Diego County. Sightings have occurred in Borrego Valley, Lakeside, Warner Springs, and El Centro [1].

List Status

CESA- Threatened [2].

Habitat Affinities

Generally found in plains, dry grasslands, and open woodlands [3]. Forages in open grasslands, small open woodlands, and sparse shrublands [3].Nesting occurs in shrublands, grasslands, riparian areas, and agricultural landscapes [4].

Taxonomy and Genetics

There are no recognized subspecies [5].

Seasonal Activity

Migration is diurnal [4]. Nearly the entire population migrates between breeding grounds in western North America to wintering grounds in the lowlands of Argentina. Overall migration can take up to 2 months (20,000km) [4]. Flocks will begin to disperse from Argentina in late February to mid-March and migrate back late August into September [6].

Life History/Reproduction

Arrival to breeding grounds begin around March or April [7]. Nest will be constructed 7-15 days after arrival and takes one or two weeks to complete [7]. Nests are typically built in trees, shrubs, or a small group of trees along a stream [8]. Young are altricial and inactive for the first 8-10 days, but able to stand at about 13-17 days. Young can feed themselves at about 23-26 days, but the female may still feed them for up to 32 days. Juveniles first attempt to fly at 29-33 days and fly at around 38-46 days [7].

Diet and Foraging

Young are fed rodents, rabbits, and reptiles [9]. However, when not breeding, adults feed almost exclusively on insects, primarily grasshoppers [9].


Pesticides are a large cause of mortality for Swainson's Hawks. Illegal shooting is also a threat to Swainson's Hawk populations [10].

Literature Sources


[1] Unitt, P. 1984b. The birds of San Diego County. San Diego Society of Natural History Museum no. 13:1-276.

[2] California Department of Fish and Wildlife, Natural Diversity Database. July 2017. Special Animals List. Periodic publication. 51 pp.

[3] Bechard, M. J. 1982. Effect of vegetative cover on foraging site selection by Swainson's Hawk. Condor no. 84:153-159

[4] Woodbridge, B. 1991. Habitat selection by nesting Swainson's Hawks: a hierarchical approach. Master's Thesis, Oregon State Univ., Corvallis.

[5] Retrieved [October, 24, 2017 ], from the Integrated Taxonomic Information System (ITIS) (

[6] Smith, N. G. 1980c. "Hawk and vulture migrations in the neotropics." In Migrant birds in the neotropics: ecology, behavior, distribution, and conservation., edited by A. Keast and E. S. Morton, 51-65. Washington, D.C: Smithsonian Inst. Press.

[7] Fitzner, R. E. 1978. Behavioral ecology of the Swainson's Hawk (Buteo swainsoni) in southeastern Washington. Phd Thesis, Washington State Univ., Pullman.

[8] McConnell, S., T. J. O'Connell and D. M. Leslie. 2008. Land cover associations of nesting territories and three sympatric budeos in shortgrass prairie. Wilson Journal of Ornithology no. 120 (4):708-716.

[9] Bechard, M.J., C.S. Houston, J.H. Sarasola, and A.S. England. 2010. Swainson’s Hawk (Buteo swainsoni). In The Birds of North America Online, No. 265 (A. Poole, Ed.). Cornell Lab of Ornithology, Ithaca, New York.

[10] Wheeler, B.K., C.M. White and J.M. Economidy. 2003. Raptors of Western North America: The Wheeler Guide.