Buteo swainsoni - Bonaparte, 1838
Swainson's Hawk
Other Common Names: Gavião-Papa-Gafanhoto
Taxonomic Status: Accepted
Related ITIS Name(s): Buteo swainsoni Bonaparte, 1838 (TSN 175367)
French Common Names: buse de Swainson
Spanish Common Names: Aguililla de Swainson, Aguilucho Langostero
Unique Identifier: ELEMENT_GLOBAL.2.105571
Element Code: ABNKC19070
Informal Taxonomy: Animals, Vertebrates - Birds - Other Birds
Image 10667

© Dick Cannings

Kingdom Phylum Class Order Family Genus
Animalia Craniata Aves Accipitriformes Accipitridae Buteo
Genus Size: D - Medium to large genus (21+ species)
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Concept Reference
Concept Reference: American Ornithologists' Union (AOU). 1998. Check-list of North American birds. Seventh edition. American Ornithologists' Union, Washington, D.C. [as modified by subsequent supplements and corrections published in The Auk]. Also available online: http://www.aou.org/.
Concept Reference Code: B98AOU01NAUS
Name Used in Concept Reference: Buteo swainsoni
Conservation Status

NatureServe Status

Global Status: G5
Global Status Last Reviewed: 06Apr2016
Global Status Last Changed: 22Nov1996
Ranking Methodology Used: Ranked by inspection
Rounded Global Status: G5 - Secure
Reasons: Large breeding range in western and central North America; winters mainly in southern South America; relatively common in some areas, but pesticide use and habitat loss in breeding and nonbreeding range have resulted in declines; recently experienced severe mortality associated with pesticide use in Argentina.
Nation: United States
National Status: N5B (19Mar1997)
Nation: Canada
National Status: N4N5B,N4N5M (08Jan2018)

U.S. & Canada State/Province Status
Due to latency between updates made in state, provincial or other NatureServe Network databases and when they appear on NatureServe Explorer, for state or provincial information you may wish to contact the data steward in your jurisdiction to obtain the most current data. Please refer to our Distribution Data Sources to find contact information for your jurisdiction.
United States Alabama (S2N), Alaska (S2S3B), Arizona (S3), Arkansas (S1B), California (S3), Colorado (S5B), Idaho (S5B), Illinois (S1), Iowa (S3B,S3N), Kansas (S4B), Minnesota (SNRB), Missouri (S2), Montana (S4B), Navajo Nation (S1B), Nebraska (S4), Nevada (S2B), New Jersey (SNA), New Mexico (S4B,S4N), North Dakota (SU), Oklahoma (S3B), Oregon (S3B), South Dakota (S4B), Texas (S4B), Utah (S3B), Washington (S3S4B), Wyoming (S4B)
Canada Alberta (S4B), British Columbia (S2B), Manitoba (S3B), Northwest Territories (SU), Ontario (SNA), Saskatchewan (S4B), Yukon Territory (S1B)

Other Statuses

IUCN Red List Category: LC - Least concern
Convention on International Trade in Endangered Species Protection Status (CITES): Appendix II

NatureServe Global Conservation Status Factors

Range Extent: >2,500,000 square km (greater than 1,000,000 square miles)
Range Extent Comments: BREEDS: known to have bred in east-central Alaska east into Yukon Territory and extreme northwestern Mackenzie; central Alberta, central Saskatchewan, southern Manitoba, western and southern Minnesota, and western Illinois south (mainly east of Cascades and Sierra Nevada) to southern California (rarely), Baja California (formerly), Sonora, Durango, Chihuahua, central and southern Texas and western Missouri; eastern breeding limits unstable. WINTERS: according to AOU (1983), primarily on pampas of southern South America (south to Uruguay and Argentina), irregularly north to Costa Rica and Panama, casually or irregularly north to the southwestern U.S. (especially Texas) and southern Florida.

Number of Occurrences: 21 to >300
Number of Occurrences Comments: No exact figures.

Population Size: 10,000 to >1,000,000 individuals
Population Size Comments: Guesstimated number of breeding pairs in Canada in the early 1990s was 20,000-50,000 (Kirk et al. 1995). Total population may be 350,000-400,000 individuals.

Overall Threat Impact Comments: In California, threats include expansion of cropland unsuitable for foraging (see GHABCOM) and residential and commercial development in former agricultural and grassland areas. In California, Risebrough et al. (1989) concluded that organochlorine contamination of eggs, mortality during migration, and toxic contamination and habitat loss on wintering grounds did not account for a decline of more than 90%. However, widespread use of pesticides and rodenticides throughout the range is cause for concern (California Department of Fish and Game 1990, Kirk and Houston 1995). For example, in early 1996, thousands (perhaps well over 20,000) died as a result of pesticide (Monocrotophos and others) spraying for grasshopper control in croplands in Argentina; those dead were predominantly adults (subadult winter range is unknown); among the dead were hawks banded in Alberta, Saskatchewan, Colorado, Idaho, and California (Geoff Holroyd, Canadian Wildlife Service). Reduced prey populations and shooting possibly are significant threats in Central and South America (Kirk and Houston 1995). See Bednarz and Hoffman (1988) for threats in New Mexico.
Easily disturbed during nesting; often abandons nest if disturbed before the eggs hatch (Biosystems Analysis 1989).

Short-term Trend Comments: Numbers have declined in the western U.S. (Terres 1980); about half of the former breeding range in California is now vacant (Palmer 1988). See Bednarz (1988) for information on status in the southwestern U.S., Bednarz and Hoffman (1988) for status in New Mexico. Recent declines in productivity have been noted in Canada (Kirk and Houston 1995). Remains common in some areas of the Great Plains.

Other NatureServe Conservation Status Information

Protection Needs: Ensure availability of nesting sites in conjunction with suitable foraging habitat.

Global Range: (>2,500,000 square km (greater than 1,000,000 square miles)) BREEDS: known to have bred in east-central Alaska east into Yukon Territory and extreme northwestern Mackenzie; central Alberta, central Saskatchewan, southern Manitoba, western and southern Minnesota, and western Illinois south (mainly east of Cascades and Sierra Nevada) to southern California (rarely), Baja California (formerly), Sonora, Durango, Chihuahua, central and southern Texas and western Missouri; eastern breeding limits unstable. WINTERS: according to AOU (1983), primarily on pampas of southern South America (south to Uruguay and Argentina), irregularly north to Costa Rica and Panama, casually or irregularly north to the southwestern U.S. (especially Texas) and southern Florida.

U.S. States and Canadian Provinces

Due to latency between updates made in state, provincial or other NatureServe Network databases and when they appear on NatureServe Explorer, for state or provincial information you may wish to contact the data steward in your jurisdiction to obtain the most current data. Please refer to our Distribution Data Sources to find contact information for your jurisdiction.
Color legend for Distribution Map
NOTE: The maps for birds represent the breeding status by state and province. In some jurisdictions, the subnational statuses for common species have not been assessed and the status is shown as not-assessed (SNR). In some jurisdictions, the subnational status refers to the status as a non-breeder; these errors will be corrected in future versions of these maps. A species is not shown in a jurisdiction if it is not known to breed in the jurisdiction or if it occurs only accidentally or casually in the jurisdiction. Thus, the species may occur in a jurisdiction as a seasonal non-breeding resident or as a migratory transient but this will not be indicated on these maps. See other maps on this web site that depict the Western Hemisphere ranges of these species at all seasons of the year.
Endemism: occurs (regularly, as a native taxon) in multiple nations

U.S. & Canada State/Province Distribution
United States AK, AL, AR, AZ, CA, CO, IA, ID, IL, KS, MN, MO, MT, ND, NE, NJ, NM, NN, NV, OK, OR, SD, TX, UT, WA, WY
Canada AB, BC, MB, NT, ON, SK, YT

Range Map
Note: Range depicted for New World only. The scale of the maps may cause narrow coastal ranges or ranges on small islands not to appear. Not all vagrant or small disjunct occurrences are depicted. For migratory birds, some individuals occur outside of the passage migrant range depicted. For information on how to obtain shapefiles of species ranges see our Species Mapping pages at www.natureserve.org/conservation-tools/data-maps-tools.

Range Map Compilers: NatureServe, 2002; WILDSPACETM 2002

U.S. Distribution by County Help
State County Name (FIPS Code)
AZ Cochise (04003), Coconino (04005), Graham (04009), Maricopa (04013), Mohave (04015), Navajo (04017), Pima (04019), Pinal (04021), Yavapai (04025)
CA Alameda (06001), Butte (06007), Colusa (06011), Contra Costa (06013), Fresno (06019), Glenn (06021), Inyo (06027), Kern (06029), Kings (06031), Lassen (06035), Los Angeles (06037), Madera (06039), Marin (06041)*, Merced (06047), Modoc (06049), Mono (06051), Monterey (06053)*, Napa (06055), Orange (06059)*, Placer (06061), Plumas (06063), Riverside (06065)*, Sacramento (06067), San Benito (06069)*, San Bernardino (06071)*, San Diego (06073)*, San Joaquin (06077), San Luis Obispo (06079), Santa Barbara (06083)*, Santa Clara (06085), Sierra (06091), Siskiyou (06093), Solano (06095), Sonoma (06097)*, Stanislaus (06099), Sutter (06101), Tehama (06103), Tulare (06107), Yolo (06113), Yuba (06115)
IA Black Hawk (19013), Fayette (19065)*, Osceola (19143)
ID Ada (16001), Adams (16003), Bannock (16005), Bear Lake (16007), Bingham (16011), Blaine (16013), Boise (16015), Bonneville (16019), Boundary (16021), Butte (16023), Camas (16025), Canyon (16027), Caribou (16029), Cassia (16031), Clark (16033), Custer (16037), Elmore (16039), Franklin (16041), Fremont (16043), Gem (16045), Gooding (16047), Idaho (16049), Jefferson (16051), Jerome (16053), Latah (16057), Lemhi (16059), Lincoln (16063), Madison (16065), Minidoka (16067), Nez Perce (16069), Oneida (16071), Owyhee (16073), Payette (16075), Power (16077), Teton (16081), Twin Falls (16083), Valley (16085), Washington (16087)
IL Kane (17089), Mchenry (17111)
MO Bates (29013), Greene (29077)
ND Grand Forks (38035), Stark (38089), Walsh (38099)*
NE Adams (31001), Arthur (31005), Banner (31007), Blaine (31009), Box Butte (31013), Chase (31029), Cherry (31031), Cheyenne (31033), Dawes (31045), Deuel (31049), Dixon (31051), Dundy (31057), Garden (31069), Grant (31075), Hamilton (31081), Holt (31089), Kearney (31099)*, Keith (31101), Kimball (31105), Lincoln (31111), Madison (31119), Morrill (31123), Perkins (31135), Pierce (31139), Platte (31141), Sheridan (31161), Sioux (31165), York (31185)
NM Dona Ana (35013), Lincoln (35027), Otero (35035), Sierra (35051), Socorro (35053)
NV Churchill (32001), Elko (32007), Eureka (32011), Humboldt (32013), Lander (32015)
OK Cimarron (40025), Jackson (40065), Murray (40099), Texas (40139), Tillman (40141)
OR Baker (41001), Crook (41013), Gilliam (41021), Harney (41025), Jefferson (41031), Lake (41037)*, Morrow (41049), Sherman (41055), Umatilla (41059), Union (41061), Wallowa (41063), Wasco (41065)
SD Bennett (46007), Brule (46015), Butte (46019), Campbell (46021), Corson (46031), Custer (46033), Davison (46035), Day (46037), Deuel (46039), Dewey (46041), Douglas (46043), Edmunds (46045), Fall River (46047), Faulk (46049), Hamlin (46057), Harding (46063), Hughes (46065), Hyde (46069), Jackson (46071), Jones (46075), Lake (46079), Lyman (46085), Marshall (46091), McPherson (46089), Meade (46093), Pennington (46103), Perkins (46105), Potter (46107), Roberts (46109), Spink (46115), Stanley (46117), Sully (46119), Tripp (46123)
UT Beaver (49001)*, Box Elder (49003), Cache (49005), Carbon (49007), Duchesne (49013), Grand (49019), Iron (49021), Juab (49023), Millard (49027), Piute (49031)*, Rich (49033), Salt Lake (49035), San Juan (49037), Sanpete (49039), Sevier (49041), Summit (49043)*, Tooele (49045), Uintah (49047), Utah (49049), Wasatch (49051), Washington (49053), Weber (49057)
WA Adams (53001), Benton (53005), Columbia (53013), Douglas (53017), Franklin (53021), Garfield (53023), Grant (53025), Kittitas (53037), Klickitat (53039), Lincoln (53043), Walla Walla (53071), Whitman (53075), Yakima (53077)
WY Albany (56001), Big Horn (56003), Campbell (56005), Carbon (56007), Converse (56009), Crook (56011), Fremont (56013), Goshen (56015), Hot Springs (56017), Johnson (56019), Laramie (56021), Lincoln (56023), Natrona (56025), Niobrara (56027), Park (56029), Platte (56031), Sheridan (56033), Sublette (56035), Sweetwater (56037), Teton (56039), Uinta (56041), Washakie (56043), Weston (56045)
* Extirpated/possibly extirpated
U.S. Distribution by Watershed Help
Watershed Region Help Watershed Name (Watershed Code)
07 Upper Minnesota (07020001)+, Lac Qui Parle (07020003)+, Turkey (07060004)+*, Middle Cedar (07080205)+, Kishwaukee (07090006)+, Upper Fox (07120006)+, Lower Fox (07120007)+*
09 Turtle (09020307)+, Park (09020310)+*
10 Yellowstone Headwaters (10070001)+, Clarks Fork Yellowstone (10070006)+, Upper Wind (10080001)+, Little Wind (10080002)+, Popo Agie (10080003)+, Muskrat (10080004)+, Lower Wind (10080005)+, Badwater (10080006)+, Upper Bighorn (10080007)+, Nowood (10080008)+, Greybull (10080009)+, Big Horn Lake (10080010)+, Dry (10080011)+, North Fork Shoshone (10080012)+, South Fork Shoshone (10080013)+, Shoshone (10080014)+, Little Bighorn (10080016)+, Upper Tongue (10090101)+, Middle Fork Powder (10090201)+, Upper Powder (10090202)+, South Fork Powder (10090203)+, Salt (10090204)+, Crazy Woman (10090205)+, Clear (10090206)+, Middle Powder (10090207)+, Little Powder (10090208)+, Upper Little Missouri (10110201)+, Antelope (10120101)+, Dry Fork Cheyenne (10120102)+, Upper Cheyenne (10120103)+, Lance (10120104)+, Lightning (10120105)+, Angostura Reservoir (10120106)+, Beaver (10120107)+, Hat (10120108)+, Middle Cheyenne-Spring (10120109)+, Rapid (10120110)+, Middle Cheyenne-Elk (10120111)+, Cherry (10120113)+, Upper Belle Fourche (10120201)+, Lower Belle Fourche (10120202)+, Redwater (10120203)+, Upper Lake Oahe (10130102)+, Lower Lake Oahe (10130105)+, West Missouri Coteau (10130106)+, Upper Heart (10130202)+, Cedar (10130205)+, North Fork Grand (10130301)+, South Fork Grand (10130302)+, Grand (10130303)+, South Fork Moreau (10130304)+, Upper Moreau (10130305)+, Lower Moreau (10130306)+, Fort Randall Reservoir (10140101)+, Bad (10140102)+, Medicine Knoll (10140103)+, Medicine (10140104)+, Upper White (10140201)+, Middle White (10140202)+, Little White (10140203)+, Lower White (10140204)+, Niobrara Headwaters (10150002)+, Upper Niobrara (10150003)+, Middle Niobrara (10150004)+, Snake (10150005)+, Upper James (10160003)+, Elm (10160004)+, East Missouri Coteau (10160007)+, Snake (10160008)+, Turtle (10160009)+, Lower James (10160011)+, Lewis and Clark Lake (10170101)+, Vermillion (10170102)+, Middle Big Sioux Coteau (10170201)+, Upper Big Sioux (10170202)+, Rock (10170204)+, Upper North Platte (10180002)+, Pathfinder-Seminoe Reservoirs (10180003)+, Medicine Bow (10180004)+, Little Medicine Bow (10180005)+, Sweetwater (10180006)+, Middle North Platte-Casper (10180007)+, Glendo Reservoir (10180008)+, Middle North Platte-Scotts Bluff (10180009)+, Upper Laramie (10180010)+, Lower Laramie (10180011)+, Horse (10180012)+, Pumpkin (10180013)+, Lower North Platte (10180014)+, Cache La Poudre (10190007)+, Lone Tree-Owl (10190008)+, Crow (10190009)+, Upper Lodgepole (10190015)+, Lower Lodgepole (10190016)+, Sidney Draw (10190017)+, Lower South Platte (10190018)+, Middle Platte-Buffalo (10200101)+, Lower Platte-Shell (10200201)+, Upper Middle Loup (10210001)+, Dismal (10210002)+, Upper North Loup (10210006)+, Calamus (10210008)+, Loup (10210009)+, Upper Elkhorn (10220001)+, North Fork Elkhorn (10220002)+, Logan (10220004)+, Little Sioux (10230003)+, North Fork Republican (10250002)+, Frenchman (10250005)+, Stinking Water (10250006)+, Upper Big Blue (10270201)+, West Fork Big Blue (10270203)+, Upper Little Blue (10270206)+*, Lower Marais Des Cygnes (10290102)+
11 James (11010002)+, Upper Cimarron (11040002)+, Upper Beaver (11100101)+, Middle Beaver (11100102)+, Coldwater (11100103)+, Lower Salt Fork Red (11120202)+, Blue-China (11130102)+, West Cache (11130203)+, Middle Washita (11130303)+
13 Jornada Del Muerto (13020210)+, Tularosa Valley (13050003)+
14 Westwater Canyon (14030001)+, Upper Green (14040101)+, New Fork (14040102)+, Upper Green-Slate (14040103)+, Big Sandy (14040104)+, Bitter (14040105)+, Upper Green-Flaming Gorge Reservoir (14040106)+, Blacks Fork (14040107)+, Muddy (14040108)+, Vermilion (14040109)+, Great Divide closed basin (14040200)+, Little Snake (14050003)+, Muddy (14050004)+, Lower White (14050007)+, Lower Green-Diamond (14060001)+, Ashley-Brush (14060002)+*, Duchesne (14060003)+, Strawberry (14060004)+, Willow (14060006)+*, Price (14060007)+, Lower San Juan-Four Corners (14080201)+
15 Havasu Canyon (15010004)+, Hualapai Wash (15010007)+, Upper Virgin (15010008)+, Lower Virgin (15010010)+, Detrital Wash (15010014)+, Middle Little Colorado (15020008)+, Cottonwood Wash (15020011)+, Polacca Wash (15020013)+*, Piute Wash (15030102)+*, Sacramento Wash (15030103)+, Upper Gila-San Carlos Reservoir (15040005)+, San Simon (15040006)+, Willcox Playa (15050201)+, Upper San Pedro (15050202)+, Lower San Pedro (15050203)+, Upper Santa Cruz (15050301)+, Lower Santa Cruz (15050303)+, Brawley Wash (15050304)+, Upper Verde (15060202)+, Agua Fria (15070102)+, Rio De La Concepcion (15080200)+, Whitewater Draw (15080301)+, San Bernardino Valley (15080302)+
16 Upper Bear (16010101)+, Central Bear (16010102)+, Bear Lake (16010201)+, Middle Bear (16010202)+, Little Bear-Logan (16010203)+, Lower Bear-Malad (16010204)+, Upper Weber (16020101)+, Lower Weber (16020102)+, Utah Lake (16020201)+, Spanish Fork (16020202)+, Provo (16020203)+, Jordan (16020204)+, Hamlin-Snake Valleys (16020301)+*, Pine Valley (16020302)+*, Rush-Tooele Valleys (16020304)+, Skull Valley (16020305)+, Southern Great Salt Lake Desert (16020306)+, Northern Great Salt Lake Desert (16020308)+, Curlew Valley (16020309)+, Middle Sevier (16030003)+, San Pitch (16030004)+, Lower Sevier (16030005)+, Escalante Desert (16030006)+, Beaver Bottoms-Upper Beaver (16030007)+*, Lower Beaver (16030008)+, Middle Humboldt (16040105)+, Little Humboldt (16040109)+, Smoke Creek Desert (16040203)+*, Carson Desert (16050203)+, East Walker (16050301)+*, Fish Lake-Soda Spring Valleys (16060010)+*, Ivanpah-Pahrump Valleys (16060015)+*
17 Lower Kootenai (17010104)+, Moyie (17010105)+, Franklin D. Roosevelt Lake (17020001)+, Chief Joseph (17020005)+, Upper Columbia-Entiat (17020010)+, Moses Coulee (17020012)+, Upper Crab (17020013)+, Banks Lake (17020014)+, Lower Crab (17020015)+, Upper Columbia-Priest Rapids (17020016)+, Upper Yakima (17030001)+, Lower Yakima, Washington (17030003)+, Snake headwaters (17040101)+, Gros Ventre (17040102)+, Greys-Hobock (17040103)+, Palisades (17040104)+, Salt (17040105)+, Idaho Falls (17040201)+, Upper Henrys (17040202)+, Lower Henrys (17040203)+, Teton (17040204)+, Willow (17040205)+, American Falls (17040206)+, Blackfoot (17040207)+, Portneuf (17040208)+, Lake Walcott (17040209)+, Raft (17040210)+, Goose (17040211)+, Upper Snake-Rock (17040212)+, Salmon Falls (17040213)+, Beaver-Camas (17040214)+, Medicine Lodge (17040215)+, Little Lost (17040217)+, Big Lost (17040218)+, Big Wood (17040219)+, Camas (17040220)+, Little Wood (17040221)+, C. J. Idaho (17050101)+, Bruneau (17050102)+, Middle Snake-Succor (17050103)+, Upper Owyhee (17050104)+, Middle Owyhee (17050107)+, Jordan (17050108)+, Boise-Mores (17050112)+, South Fork Boise (17050113)+, Lower Boise (17050114)+, Middle Snake-Payette (17050115)+, South Fork Payette (17050120)+, Payette (17050122)+, North Fork Payette (17050123)+, Weiser (17050124)+, Brownlee Reservoir (17050201)+, Burnt (17050202)+, Powder (17050203)+, Hells Canyon (17060101)+, Imnaha (17060102)+, Upper Grande Ronde (17060104)+, Wallowa (17060105)+, Lower Grande Ronde (17060106)+, Lower Snake-Tucannon (17060107)+, Palouse (17060108)+, Rock (17060109)+, Lower Snake (17060110)+, Upper Salmon (17060201)+, Middle Salmon-Panther (17060203)+, Lemhi (17060204)+, Upper Middle Fork Salmon (17060205)+, South Fork Salmon (17060208)+, Lower Salmon (17060209)+, Little Salmon (17060210)+, Clearwater (17060306)+, Middle Columbia-Lake Wallula (17070101)+, Walla Walla (17070102)+, Umatilla (17070103)+, Willow (17070104)+, Middle Columbia-Hood (17070105)+*, Klickitat (17070106)+, Lower John Day (17070204)+, Upper Deschutes (17070301)+*, Beaver-South Fork (17070303)+*, Upper Crooked (17070304)+, Lower Deschutes (17070306)+, Trout (17070307)+, Harney-Malheur Lakes (17120001)+, Silvies (17120002)+, Silver (17120004)+, Summer Lake (17120005)+*, Alvord Lake (17120009)+
18 Lost (18010204)+, Butte (18010205)+, Shasta (18010207)+, Upper Pit (18020002)+, Sacramento-Stone Corral (18020104)+, Lower American (18020111)+, Upper Stony (18020115)+, Upper Cache (18020116)+, Middle Fork Feather (18020123)+, Upper Yuba (18020125)+, Upper Bear (18020126)+, Thomes Creek-Sacramento River (18020156)+, Big Chico Creek-Sacramento River (18020157)+, Butte Creek (18020158)+, Honcut Headwaters-Lower Feather (18020159)+, Upper Coon-Upper Auburn (18020161)+, Upper Putah (18020162)+, Lower Sacramento (18020163)+, Upper Kern (18030001)+, Middle Kern-Upper Tehachapi- (18030003)+, Upper Poso (18030004)+*, Upper Deer-Upper White (18030005)+, Upper Tule (18030006)+, Upper Kaweah (18030007)+, Upper Dry (18030009)+, Tulare-Buena Vista Lakes (18030012)+, Middle San Joaquin-Lower (18040001)+, Middle San Joaquin-Lower (18040002)+, San Joaquin Delta (18040003)+, Upper Chowchilla-Upper Fresno (18040007)+, Upper Merced (18040008)+, Upper Tuolumne (18040009)+, Upper Stanislaus (18040010)+, Upper Calaveras (18040011)+, Upper Mokelumne (18040012)+, Upper Cosumnes (18040013)+, Panoche-San Luis Reservoir (18040014)+*, Rock Creek-French Camp Slough (18040051)+, Suisun Bay (18050001)+, San Pablo Bay (18050002)+, Coyote (18050003)+, Pajaro (18060002)+*, Estrella (18060004)+, Salinas (18060005)+*, Cuyama (18060007)+, Santa Maria (18060008)+*, Santa Clara (18070102)+*, Santa Monica Bay (18070104)+*, Los Angeles (18070105)+*, San Gabriel (18070106)+*, Seal Beach (18070201)+*, Santa Ana (18070203)+*, Santa Margarita (18070302)+*, San Luis Rey-Escondido (18070303)+*, San Diego (18070304)+*, Surprise Valley (18080001)+, Madeline Plains (18080002)+, Honey-Eagle Lakes (18080003)+, Mono Lake (18090101)+*, Crowley Lake (18090102)+, Owens Lake (18090103)+, Antelope-Fremont Valleys (18090206)+, Mojave (18090208)+*
+ Natural heritage record(s) exist for this watershed
* Extirpated/possibly extirpated
Ecology & Life History
Basic Description: A large soaring bird (hawk).
Reproduction Comments: Egg dates: mainly April-May in southwestern U.S., California, and Oregon; mainly May-June in central plains states and Canada. Clutch size usually is 2-3. Incubation lasts 34-35 days per egg, almost exclusively by female (male provides food). Young are tended by both adults, leave nest in about 30 days, attain flight at 42-44 days (around 3rd week in July in southwestern U.S.), dependent on parents for 4-4.5 weeks after fledging. First breeds at 2 years. Usually 0.1-0.2 pairs per sq km; average of 1.4-2.4 km between nests. See Bednarz (1988) for information on reproduction in New Mexico. Reported nest density throughout range varies from 0.08-1.61 nests per sq km.
Ecology Comments: May form premigratory aggregations in summer. Nesting density in suitable habitat varies throughout range from 0.1-1.6 nests per 10 sq km (Bednarz and Hoffman 1988); nests average 1.4-2.4 km apart (see Rothfels and Lein 1983). At one site in California, five nests typically found along a 1 km riparian strip, the nearest nests only 60 meters apart (England et al. 1997). Home ranges during breeding season vary greatly--from 69 to 8718 hectares (reviewed in England et al. 1997). Interspecific territoriality with Red-tailed Hawk in some areas; in other areas may compete with Ferruginous Hawk or be limited by presence of and predation by Great Horned Owl (Palmer 1988).

In California, dispersal distances from natal sites to subsequent breeding sites ranged from 0 to 18 kilometers, mean 8.8 kilometers (Woodbridge et al. 1995). In contrast, none of 697 banded nestlings in Saskatchewan returned to the study area; three were found 190, 200 and 310 kilometers away (Houston and Schmutz 1995).

Non-Migrant: N
Locally Migrant: N
Long Distance Migrant: Y
Mobility and Migration Comments: In migration, occurs regularly in most of Middle America, and rarely east along the Gulf Coast to Florida (AOU 1983). In California, migrates March-early May, with a peak in the first half of April, and September-October (Biosystems Analysis, Inc. 1989). Migrants are greatly concentrated as they pass through Panama (mostly March-early April and October-early November; Ridgely and Gwynne 1989). Migrates through Costa Rica late September-November and late February-early May (Stiles and Skutch 1989). In Colombia, flocks of various sizes reported mainly February-March and September-early November (Hilty and Brown 1986). Main northward migration passes through Panama in mid-March, Veracruz in latter half of March and early April, southern Texas and southwstern U.S. chiefly in April (Palmer 1988); fall concentrations and movements occur in August-September in the north, mainly early October in Texas; peak in migration occurs in September in the southwestern U.S.; arrives in Argentina in late November (Palmer 1988). Annual migration flight may be 18,000-27,000 km, encompasses 4 months of the year. See Houston (1990) for information on migrations of Saskatchewan breeders. Migrates in large, often immense, flocks. Migrates over terrain where updrafts provide needed buoyancy for soaring. May roost at night on ground during migration.
Palustrine Habitat(s): Riparian
Terrestrial Habitat(s): Cropland/hedgerow, Desert, Grassland/herbaceous, Savanna, Woodland - Mixed
Habitat Comments: Savanna, open pine-oak woodland and cultivated lands (e.g., alfalfa and other hay crops, and certain grain and row croplands) with scattered trees. Tolerates extensive cultivation in nesting area (Schmutz 1989), though vineyards, orchards, rice, corn, and cotton are not suitable foraging habitat. In migration and winter also in grasslands and other open country (AOU 1983). Migrants may roost at night on ground in very large fields (Ridgely and Gwynne 1989). Nests typically in solitary tree, bush, or small grove; many nests on old black-billed magpie nests; sometimes on rock ledge. Readily nests in trees in shelterbelts and similar situations produced by humans (Gilmer and Stewart 1984). Recently reported nesting in city trees and on railway signal gantry in Regina, Saskatchewan (Condor 94:773-774). In the Central Valley of California, nests often are within one mile of a riparian zone; Great Basin nests, usually in junipers, are not near riparian zones (Biosystems Analysis, Inc. 1989). Evidently often returns to area where it nested in previous year.

Swainson's Hawks have adapted to agricultural landscapes in Nevada. An ideal landscape for the Swainson's Hawk provides large riparian nesting trees, agricultural fields, and open shrublands within relatively close proximity (GBBO 2010). Swainson's Hawks in the Great Basin occupy the Juniper/Sagebrush community typical to the area. In California, Swainson's hawk habitat generally consists of large, flat, open, undeveloped landscapes that include suitable grassland or agricultural foraging habitat and sparsely distributed trees for nesting (England et al. 1997). Populations in the Great Basin often use juniper trees (Juniperus sp.) for nesting (England et al. 1997), and at least three known nest sites in the Mojave Desert are in Joshua trees (Yucca brevifolia) (California Natural Diversity Database 2009) (PCCP 2010). In addition to Joshua trees, this species was also known historically from the Mojave Yukka (Yucca schidigera) and possibly desert riparian habitats (Bloom 1980).

Adult Food Habits: Carnivore, Invertivore
Immature Food Habits: Carnivore, Invertivore
Food Comments: Vertebrates (mainly mammals) dominate the diet during the breeding season; invertebrates (especially crickets and grasshoppers) are common food at other times and sometimes for nonbreeders in summer. Hawks wintering in Argentina ate mainly dragonflies (Condor 95:475-479, Wilson Bull. 105:365-366). Mammals consumed often include young ground squirrels and pocket gophers. Depending on availability, also eats other small mammals, snakes, lizards, birds, amphibians, and some carrion (e.g., road kills). Hunts for insects on ground; may also catch insects in air. Hunts while soaring or from perch. Does not feed during most of migration (occasional feeding during initial and terminal stages) (Palmer 1988).
Adult Phenology: Diurnal
Immature Phenology: Diurnal
Length: 53 centimeters
Weight: 1069 grams
Economic Attributes Not yet assessed
Management Summary
Biological Research Needs: Determine degree of competition with B. jamaicensis.
Population/Occurrence Delineation
Group Name: Hawks and Falcons

Use Class: Breeding
Subtype(s): Feeding Area, Nest Site
Minimum Criteria for an Occurrence: Evidence of historical breeding, or current and likely recurring breeding, at a given location, minimally a reliable observation of one or more breeding pairs in appropriate habitat. Be cautious about creating EOs for observations that may represent single breeding events outside the normal breeding distribution.
Mapping Guidance: If nest site is separated from feeding area by more than 100 meters, map as separate polygons.
Separation Barriers: None.
Separation Distance for Unsuitable Habitat: 10 km
Separation Distance for Suitable Habitat: 10 km
Separation Justification: Separation distance a compromise between usually relatively small home ranges and obvious mobility of these birds. Home ranges variable, ranging from about 0.5 to about 90 square kilometers; the latter figure refers to nests where birds commuted some distance to feeding grounds. A number of studies give mean home ranges on the order of 7 square kilometers, which equates to a circle with a diameter of about 3 kilometers; three times that home range gives a separation distance of about 10 kilometers. Home ranges: Ferruginous Hawk, mean 5.9 square kilometers in Utah (Smith and Murphy 1973); range 2.4 to 21.7 square kilometers, mean 7.0 square kilometers in Idaho (Olendorff 1993); mean 7.6 square kilometers in Idaho (McAnnis 1990); mean 90 square kilometers in Washington (Leary et al. 1998); Red-tailed Hawk, most forage within 3 kilometers of nest (Kochert 1986); mean spring and summer male home ranges 148 hectares (Petersen 1979); Hawaiian Hawk, 48 to 608 hectares (n = 16; Clarkson and Laniawe 2000); Zone-tailed Hawk, little information, apparent home range 1-2 kilometers/pair in west Texas (Johnson et al. 2000); White tailed Kite, rarely hunts more than 0.8 kilometers from nest (Hawbecker 1942); Prairie Falcon, 26 square kilometers in Wyoming (Craighead and Craighead 1956), 59 to 314 square kilometers (reported by Steenhof 1998); Aplomado Falcon, 2.6 to 9.0 square kilometers (n = 5, Hector 1988), 3.3 to 21.4 square kilometers (n = 10, Montoya et al. 1997). Nest site fidelity: high in Zone-tailed Hawk; all seven west Texas nesting territories occupied in 1975 were reused in 1976 (Matteson and Riley 1981). Swainson's Hawk: In California, dispersal distances from natal sites to subsequent breeding sites ranged from 0 to 18 kilometers, mean 8.8 kilometers (Woodbridge et al. 1995); in contrast, none of 697 nestlings in Saskatchewan returned to the study area; three were found 190, 200 and 310 kilometers away (Houston and Schmutz 1995).
Inferred Minimum Extent of Habitat Use (when actual extent is unknown): 3 km
Inferred Minimum Extent Justification: Foraging range variable; 3 kilometers is the mean diameter in several species.
Date: 13Mar2001
Author: Cannings, S.

Use Class: Nonbreeding
Subtype(s): Foraging area, Roosting area
Minimum Criteria for an Occurrence: Evidence of recurring presence of wintering birds (including historical); and potential recurring presence at a given location, usually minimally a reliable observation of 5 birds (this can be reduced to 1 individual for rarer species). Occurrences should be locations where the species is resident for some time during the appropriate season; it is preferable to have observations documenting presence over at least 20 days annually. Be cautious about creating EOs for observations that may represent single events.
Separation Barriers: None.
Separation Distance for Unsuitable Habitat: 10 km
Separation Distance for Suitable Habitat: 10 km
Separation Justification: Separation distance somewhat arbitrary; set at 10 kilometers to define occurrences of managable size for conservation purposes. However, occurrences defined primarily on the basis of areas supporting concentrations of foraging birds, rather than on the basis of distinct populations.
Date: 15Apr2002
Author: Cannings, S.
Population/Occurrence Viability
U.S. Invasive Species Impact Rank (I-Rank) Not yet assessed
NatureServe Conservation Status Factors Edition Date: 15Feb1996
NatureServe Conservation Status Factors Author: Hammerson, G.
Element Ecology & Life History Edition Date: 30Mar1995
Element Ecology & Life History Author(s): Hammerson, G.

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  • USGS. 2008a. Alaska Off-road Breeding Bird Survey: Database of Bird Distribution (ALMS). Available online at http://www.absc.usgs.gov/research/bpif/OBS/database/index.html. (Accessed 5/15/2008).

  • Wauer, R. H., and D. L. Carter. 1965. Birds of Zion national Park and vicinity. Zion Nat. Hist. Assoc., Springdale, UT. 92 pp.

  • Woodbridge, B., K. K. Finley, and P. H. Bloom. 1995. Reproductive performance, age structure, and natal dispersal of Swainson's Hawks in the Butte Valley, California. Journal of Raptor Research 29:187-192.

  • 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.

  • Yukon Bird Club. 1995. Yukon Warbler: Newsletter of the Yukon Bird Club - Fall 1995. 20pp.

  • Yukon Bird Club. 1997. Yukon Warbler: Newsletter of the Yukon Bird Club - Winter 1997. 36pp.

  • Yukon Bird Club. 2002. Yukon Warbler: Newsletter of the Yukon Bird Club - Spring 2002. 16pp.

  • Yukon Bird Club. 2008. Yukon Warbler: Newsletter of the Yukon Bird Club - Fall 2008. 26pp.

  • Yukon Bird Club. 2009. Yukon Warbler: Newsletter of the Yukon Bird Club - Spring 2009. 36pp.

  • Yukon Bird Club. 2010. Yukon Warbler: Newsletter of the Yukon Bird Club - Spring 2010. 30pp.

  • Yukon Bird Club. 2014. Yukon Warbler: Newsletter of the Yukon Bird Club - Spring 2014. 12pp.

  • Zook, J. L. 2002. Distribution maps of the birds of Nicaragua, Costa Rica, and Panama. Unpublished.

  • eBird. 2016. eBird: An online database of bird distribution and abundance [web application]. eBird, Cornell Lab of Ornithology, Ithaca, New York. Available: http://www.ebird.org. Accessed in 2016.

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Ridgely, R.S., T.F. Allnutt, T. Brooks, D.K. McNicol, D.W. Mehlman, B.E. Young, and J.R. Zook. 2003. Digital Distribution Maps of the Birds of the Western Hemisphere, version 1.0. NatureServe, Arlington, Virginia, USA.

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"Data provided by NatureServe in collaboration with Bruce Patterson, Wes Sechrest, Marcelo Tognelli, Gerardo Ceballos, The Nature Conservancy-Migratory Bird Program, Conservation International-CABS, World Wildlife Fund-US, and Environment Canada-WILDSPACE."

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