Illinois Natural History Survey - University of Illinois

Swainson's hawk
Buteo swainsoni

 

Taxonomy
Occurence in Illinois
Status
Habitat associations
Guilds
Food-habits
Environmental associations
Life history
Management practices
References


TAXONOMY

 

  • Phylum: Chordata
  • Class: Aves
  • Order: Falconiformes
  • Family: Accipitridae
  • Genus: Buteo
  • Species: Buteo swainsoni
  • Authority: Bonaparte

OCCURENCE IN ILLINOIS

No comments.

 


STATUS

Items in bold indicate applicable categories
Forest Service Categories: S = recommended for regional sensitive status, F = forest listed species, M = management indicator species

Federal Status:

Endangered Threatened Proposed for listing
Candidate for proposal Recovery plan approved Recovery plan received (USFWS)
Recovery plan in preparation Under notice of review Delisted
Migratory EPA indicator Forest Serv.- Shawnee species

State Status:

Endangered Threatened Proposed

Other:

Game Furbearer Nongame protected
Sportfish Commercial Pest None of the above

Comments on status:
A western U.S. species; uncommon nester in IL. *15,17*. B. swainsonni is currently being considered for federal listing under category 2, federal register, vol. 47, 1982 *22*.

 


HABITAT ASSOCIATIONS

Items in bold indicate applicable categories

General habitat:

Unknown Terrestrial Aquatic Riparian

USFS timber inventory forest size class:

Unknown Unstocked Seedling Sapling
Seedling/sapling Pole Mature Over mature

Land use and land cover:

Unknown   Urban Residential
Commercial
Industrial
Transportation, communication
Complex industrial/commercial
Mixed
Other
Agricultural Crop, pasture
Orchards, groves, nurseries

Feedlot
Other
Rangeland Herbaceous
Shrub and brush
Mixed
Forestland Deciduous
Evergreen
Mixed
Water Stream
Lake
Reservoir
Bay
Wetland Forest
Non-forest
Barren Salt flat
Beach
Sand
Rock
Mine
Transit
Mix

 


Forest cover types:

Cover typeStructural stageCanopy closureSeason
Unknown Unknown Unknown Unknown

Associated tree species:

  • All

National wetland inventory classifications:

SystemSubsystemClassSubclassWater regime modifiersWater chemistry
Riverine Unknown perennial Forest Deciduous Unknown/unspecified Unknown/unspecified

High value habitats

HabitatStructural stageSeason
Cropland and pasture Not applicable
(HVAL-HAB cover)
Spring/summer
Other agricultural land Not applicable
(HVAL-HAB cover)
Spring/summer
Deciduous forest land Unknown Spring/summer
Forest Unknown Spring/summer
Upland forest Unknown Spring/summer
Prairie Special habitat Spring/summer
Savanna Mature
(9" dia. & 100 yrs. old)
Spring/summer

Species-habitat interrelations: Swainson's nest in trees along cropfields, rivers or prairies and feed in these habitats *04,09,10,14*. Savannas are important to this species in Illinois *15*. Swainson's is a rare breeding season resident *01*; the habitats discussed are those required in the nesting season.

 


GUILDS

Feed-guilding:

HabitatStructural stageSeasonFeed-guilds
Cropland and pasture Not applicable
(HVAL-HAB cover)
Spring/summer Terrestrial surface - arthropods
Air - arthropods
Terrestrial surface - amphibians
Terrestrial surface - reptiles
Terrestrial surface - birds
Air - birds
Terrestrial surface - small mammals (< 1 kg)
Other agricultural land Not applicable
(HVAL-HAB cover)
Spring/summer Terrestrial surface - arthropods
Air - arthropods
Terrestrial surface - amphibians
Terrestrial surface - reptiles
Terrestrial surface - birds
Air - birds
Terrestrial surface - small mammals (< 1 kg)
Deciduous forest land Unknown Spring/summer Terrestrial surface - arthropods
Air - arthropods
Terrestrial surface - amphibians
Terrestrial surface - reptiles
Terrestrial surface - birds
Air - birds
Terrestrial surface - small mammals (< 1 kg)
Forest Unknown Spring/summer Terrestrial surface - arthropods
Air - arthropods
Terrestrial surface - amphibians
Terrestrial surface - reptiles
Terrestrial surface - birds
Air - birds
Terrestrial surface - small mammals (< 1 kg)
Upland forest Unknown Spring/summer Terrestrial surface - arthropods
Air - arthropods
Terrestrial surface - amphibians
Terrestrial surface - reptiles
Terrestrial surface - birds
Air - birds
Terrestrial surface - small mammals (< 1 kg)
Flatwoods Unknown Spring/summer Terrestrial surface - arthropods
Air - arthropods
Terrestrial surface - amphibians
Terrestrial surface - reptiles
Terrestrial surface - birds
Air - birds
Terrestrial surface - small mammals (< 1 kg)
Prairie Special habitat Spring/summer Terrestrial surface - arthropods
Air - arthropods
Terrestrial surface - amphibians
Terrestrial surface - reptiles
Terrestrial surface - birds
Air - birds
Terrestrial surface - small mammals (< 1 kg)
Savanna Mature
(9" dia. & 100 yrs. old)
Spring/summer Terrestrial surface - arthropods
Air - arthropods
Terrestrial surface - amphibians
Terrestrial surface - reptiles
Terrestrial surface - birds
Air - birds
Terrestrial surface - small mammals (< 1 kg)

Comments on feed-guilding:
Records based primarily on information from the breeding season.

Breed-guilding:

HabitatStructural stageSeasonBreed-Guilds
Other agricultural land Not applicable
(HVAL-HAB cover)
Spring/summer Tree canopy, large branches of live broad-leaved deciduous trees
Tree canopy, large branches of dead broad-leaved deciduous trees
Deciduous forest land Unknown Spring/summer Tree canopy, large branches of live broad-leaved deciduous trees
Tree canopy, large branches of dead broad-leaved deciduous trees
Forest Unknown Spring/summer Tree canopy, large branches of live broad-leaved deciduous trees
Tree canopy, large branches of dead broad-leaved deciduous trees
Upland forest Unknown Spring/summer Tree canopy, large branches of live broad-leaved deciduous trees
Tree canopy, large branches of dead broad-leaved deciduous trees
Flatwoods Unknown Spring/summer Tree canopy, large branches of live broad-leaved deciduous trees
Tree canopy, large branches of dead broad-leaved deciduous trees
Savanna Mature
(9" dia. & 100 yrs. old)
Spring/summer Tree canopy, large branches of live broad-leaved deciduous trees
Tree canopy, large branches of dead broad-leaved deciduous trees

 


FOOD-HABITS

Trophic level is CARNIVORE

Food itemLife stage/plant part
Insecta Adult
Orthoptera (grasshoppers, crickets, cockroaches) Adult
Salientia (frogs, toads) Adult
Sauria (lizards, skinks, iguana) Adult
Leporidae (rabbits, hares) Adult
Sciuridae (squirrels, chipmunks, marmots, prairie dogs) Adult
Geomyidae (pocket gophers) Adult
Cricetidae (woodrats, mice, voles, lemmings, muskrats) Adult
Muridae (Norway rat, house mouse) Adult
Birds Adult
Important:
Orthoptera (grasshoppers, crickets, cockroaches) Adult
Sciuridae (squirrels, chipmunks, marmots, prairie dogs) Adult
Geomyidae (pocket gophers) Adult
Cricetidae (woodrats, mice, voles, lemmings, muskrats) Adult
Juvenile:
Geomyidae (pocket gophers) Adult
Cricetidae (woodrats, mice, voles, lemmings, muskrats) Adult
Birds Adult
Adult:
Insecta Adult
Orthoptera (grasshoppers, crickets, cockroaches) Adult
Salientia (frogs, toads) Adult
Sauria (lizards, skinks, iguana) Adult
Leporidae (rabbits, hares) Adult
Sciuridae (squirrels, chipmunks, marmots, prairie dogs) Adult
Geomyidae (pocket gophers) Adult
Cricetidae (woodrats, mice, voles, lemmings, muskrats) Adult
Muridae (Norway rat, house mouse) Adult
Birds Adult

Comments on food habits: 
General: Although some sources cite insects (primarily orthoptera) and cold- blooded vertebrates as important food items *04,05,08,12,18*, most recent literature suggests small mammals are most important prey *09, 10,14*.
Juvenile: No comments.
Adult: No comments.


ENVIRONMENTAL ASSOCIATIONS

General:

  • Ecotones: woodland/crop fields
  • Ecotones: woodland/old fields
  • Ecotones: woodland/water
  • Ecotones: woodland/grassland
  • Ecotones: crop field/grassland
  • Pastures: see comments
  • Grassland: see comments
  • Meadows: see comments
  • Old fields: see comments
  • Hardwood forest: see comments

Limiting:

  • Hardwood forest: see comments

Feeding juvenile:

  • Ecotones: woodland/crop fields
  • Ecotones: woodland/old fields
  • Ecotones: woodland/water
  • Ecotones: woodland/grassland
  • Ecotones: crop field/grassland
  • Pastures: see comments
  • Grassland: see comments
  • Meadows: see comments
  • Old fields: see comments
  • Hardwood forest: see comments

Resting juvenile:

  • Ecotones: woodland/crop fields
  • Ecotones: woodland/old fields
  • Ecotones: woodland/water
  • Ecotones: woodland/grassland
  • Ecotones: crop field/grassland
  • Pastures: see comments
  • Grassland: see comments
  • Meadows: see comments
  • Old fields: see comments
  • Hardwood forest: see comments

Feeding adult:

  • Ecotones: woodland/crop fields
  • Ecotones: woodland/old fields
  • Ecotones: woodland/water
  • Ecotones: woodland/grassland
  • Ecotones: crop field/grassland
  • Pastures: see comments
  • Grassland: see comments
  • Meadows: see comments
  • Old fields: see comments
  • Hardwood forest: see comments

Resting adult:

  • Ecotones: woodland/crop fields
  • Ecotones: woodland/old fields
  • Ecotones: woodland/water
  • Ecotones: woodland/grassland
  • Ecotones: crop field/grassland
  • Pastures: see comments
  • Grassland: see comments
  • Meadows: see comments
  • Old fields: see comments
  • Hardwood forest: see comments

Breeding adult:

  • Ecotones: woodland/crop fields
  • Ecotones: woodland/old fields
  • Ecotones: woodland/water
  • Ecotones: woodland/grassland
  • Ecotones: crop field/grassland
  • Hardwood forest: see comments

Comments on environmental associations:
General: Swainson's hawk lives in a variety of open lands and woodlands; seemingly available nest trees are the only limiting factor *09*.
Feeding juvenile: No comments.
Resting juvenile: No comments.
Feeding adult: No comments.
Resting adult: No comments.
Breeding adult: No comments.


LIFE HISTORY

Origin: Native *01*.

Physical description: Length 18 in., wingspread 49 in. *02*. Ave wt. males 908 gm., females 1070 gm. *03*. In dark phase, dark black- brown with basal half of tail whitish. In light phase, upper parts dark brown with whitish throat and belly, brown band across chest *04,05*.

Reproduction: Hawks return to breeding grounds (males first *12*) in U.S. mid-Mar. To mid-Apr. *08*. Mates of same color phase are preferred *06*. Territory selection by nesting pairs begins in Apr.*07*. If male dies, female will replace mate in same breeding season *12*. Male presumably begins nest building, female may assist *12*. Perhaps 50% of nests are built new each season *10*. Nest built in trees along rivers, agricultural fields, forest edges, usually 3.5-6.5 m high. No apparent preference for species of nest tree *08,09,10*. Clutch of 2-4 eggs, ave. 2-3 *04,6,12*; both parents (mostly female) incubate *04,06,08* about 28 days *04,05*. A second clutch may be laid if first is lost *06*. Young hatch at 1-2 d. intervals *08*, in mid-June in IL. *13*. Parents are not defensive of nest until after hatching *13*; even then, Swainsons are not particularly aggressive around the nest and may even allow some other bird species to nest in lower parts of their nest *08*. Nestling period 30-40 days *04,05,07*. After fledging, young begin their hunting on the ground, presumably for insects *05*. Post-fledging period 4-4.5 wk. *12*.

Behavior: Hunts from perches (trees, telephone poles, fence posts, knolls), also by soaring. Usually pounces on prey on the ground, may also eat insects and birds in the air *04,08*. Reported nesting densities (area/pr.): 6.7 sq. km. *06* and 2.4 sq. mi. *07* In wy. Home ranges: 900 ha. in WA *14*, 670 ha. in WY *06*, 2000 ha. in ND *10*. Mean distance between ND nests 2.3 km. *10*. Some references suggest Swainson's not strongly territorial or aggressive *05,08*. Conversely, a Canadian study reports aggressive encounters between nesting Swainson's hawks and ferruginous and red- tailed hawks, Swainson's being the aggressor *09*. Great horned owls and red-tailed hawks may occupy Swainson's nests - both species nest earlier *13*. Longest migration of all N. American hawks. Migrate in large flocks, often flying in concentrations along the same narrow corridors each yr. *04*. It is thought they do not eat or drink during migration *04*. Most winter in S. America *04*; a small population winters in FL and TX *20*.

Limiting factors: Interspecific competition: great horned owls and red-tailed hawks occupy Swainson's nests and nesting habitats *13*. Swainson's reproductive success decreases with decreasing distance between their nests and those of ferruginous and red-tailed hawks *09*. Disease is not an important cause of nestling mortality *07*. About 33% of nests lost are destroyed in bad weather, 20% by predation, 3% by human factors (44% unknown) in one study *10* 1/3 of all nests may be lost *06*. Human disturbance may be an important factor reducing productivity in IL *15*.

Population parameters: In two WY studies: egg loss 15% and 2.06 Young fledged/nesting pr. *06*; 40% nestling mortality and 43% fledging success in another *07* suggests a much lower productivity. In IL, productivity is seemingly declining, and Swainson's populations are considered "sporatic and declining in numbers" *15*. Longevity in wild 13 yr. *12*.

 


MANAGEMENT PRACTICES

Beneficial:

  • Maintaining undisturbed/undeveloped areas
  • Maintaining natural ecological succession
  • Developing/maintaining edge (ecotones)
  • Preserving endangered species habitat
  • Performing special survey prior to prescription
  • Performing field survey prior to prescription
  • Controlling land use and human activities
  • Seasonal restriction of human use of habitats
  • Developing/maintaining riparian habitat
  • Developing/maintaining streamside vegetation to prevent erosion and provide riparian habitat
  • Revegetating streambanks using grass-forb-sedge-tree mixtures
  • Developing/maintaining hedge rows/windbreaks

Adverse:

  • Performing special survey prior to prescription
  • Strip mining
  • Cutting and deforestation

Comments on management practices:
Nest in trees along rivers, agricultural areas, savannas, and grass- lands *08,09,10*. These areas should be maintained. Nesting birds should be protected from human disturbance *15*. Swainson's hawk is protected under the Illinois Endangered Species Act, 1972 *15*, Migratory Bird Treaty Act, 1918 *19* and Illinois Wildlife Code, 1971 *21*.

 


REFERENCES

0. BUTCHER, M.K. 1984. ILL. NAT. HIST. SURV., 607 E. PEABODY DR., CHAMPAIGN, ILL. (217)333-6846.

1. BOHLEN, H. 1978. AN ANNOTATED CHECK-LIST OF THE BIRDS OF ILLINOIS. ILLINOIS STATE MUS. POP. SCI. SER., VOL. IX. 156 P.

2. ROBBINS, C., B. BRUUN AND H. ZIM. 1966. BIRDS OF NORTH AMERICA. GOLDEN PRESS, NEW YORK. 340 P.

3. SNYDER, N.F. AND J.W. WILEY. 1976. SEXUAL SIZE DIMORPHISM IN HAWKS AND OWLS OF NORTH AMERICA. ORNITH. MONOGR. NO. 20. 96 P.

4. BROWN, L. AND D. AMADON. 1968. EAGLES, HAWKS AND FALCONS OF THE WORLD, VOL. 2. MCGRAW-HILL BOOK CO., NEW YORK. PP. 445-945.

5. TERRES, J. 1980. AUDUBON SOCIETY: ENCYCLOPEDIA OF NORTH AMERICAN BIRDS. ALFRED KNOPF, NEW YORK. 1109 P.

6. DUNKLE, S.W. 1977. SWAINSON'S HAWKS ON THE LARAMIE PLAINS, WYOMING. AUK 94:65-71.

7. CRAIGHEAD, J.J. AND F.C. CRAIGHEAD, JR. 1956. HAWKS, OWLS AND WILDLIFE. THE STACKPOLE CO., HARRISBURG, PA. 443 P.

8. BENT, A.C. 1937. LIFE HISTORIES OF NORTH AMERICAN BIRDS OF PREY. ORDER FALCONIFORMES (PART I). U.S. NATL. MUS. BULL. NO. 167.

9. SCHMUTZ, J., S. SCHMUTZ, AND D. BOOG. 1980. COEXISTENCE OF 3 SPP. OF HAWKS IN THE PRAIRIE-PARKLAND ECOTONE. CAN. J. ZOOL. 58(6):1075-1089.

10. GILMER, D.S. AND R.E. STEWART. 1984. SWAINSON'S HAWK NESTING ECOLOGY IN NORTH DAKOTA. CONDOR 86:12-18.

11. WOFFINDEN, N.D. AND J.A. MOSHER. 1979. GROUND NESTING AND AGGRESSIVE BEHAVIOR BY THE SWAINSON'S HAWK (BUTEO SWAINSONI). GREAT BASIN NAT. 39(3):253-254.

12. NEWTON, I. 1979. POPULATION ECOLOGY OF RAPTORS. BUTEO BOOKS, VERMILLION, SD. 399 P.

13. KEIR, J. AND D. WILDE. 1976. OBSERVATIONS OF SWAINSON'S HAWK NESTING IN NORTHEASTERN ILLINOIS. WILSON BULL. 88(4):658-659.

14. BECHARD, M.J. 1982. EFFECTS OF VEGETATIVE COVER ON FORAGING SITE SELECTION BY SWAINSON'S HAWK. CONDOR 84:153-159.

15. BOWLES, M.L., V.E. DIERSING, J.E. EBINGER AND H.C. SCHULTZ, EDS. 1981. ENDANGERED AND THREATENED VERTEBRATE ANIMALS AND VASCULAR PLANTS OF ILLINOIS. ILLINOIS DEPT. CONSERV. 189 P.

16. AMERICAN ORNITHOLOGISTS' UNION. 1982. THIRTY-FOURTH SUPPLEMENT TO THE AMERICAN ORNITHOLOGISTS' UNION. CHECK-LIST OF NORTH AMERICAN BIRDS. SUPPLEMENT AUK 99(3).

17. RIDGEWAY, R. 1889. THE ORNITHOLOGY OF ILLIOIS. VOL. 1. PANTAGRAPH PRINTING AND STATIONERY CO., BLOOMINGTON, ILLINOIS, 1913. 520 P.

18. FISHER, A.K. 1893. THE HAWKS AND OWLS OF THE UNITED STATES. U.S.D.A. DEPT. AGRIC. DIV. ORNITH. AND MAMMAL. BULL. NO. 3. 210 P.

19. U.S. FISH AND WILDLIFE SERVICE. 1983. TITLE 50. WILDLIFE AND FISH- ERIES. CHAPTER 1. PP.11-18. 50CFR10.13. LIST OF MIGRATORY BIRDS. SPECIAL PUBL. FEDERAL REGISTER. GENERAL SERVICES ADMIN. OCTOBER 1.

20. BROWNING, M.R. 1974. COMMENTS ON THE WINTERING DISTRIBUTION OF THE SWAINSON'S HAWK (BUTEO SWAINSONI) IN NORTH AMERICA. AMERICAN BIRDS 28:865-867.

21. ILLINOIS DEPARTMENT OF CONSERVATION. 1980. CONSERVATION LAWS. CH 61. WILDLIFE. ART II. PAR. 2.2. REPRINTED FROM ILLINOIS REVISED STATUTES, 1979. WEST PUBL. CO., ST. PAUL, MN. 120 P.

22. U.S. DEPT. OF INTERIOR, FISH AND WILDLIFE SERVICE [USDI]. 1982. ENDAN- GERED AND THREATENED WILDLIFE AND PLANTS; REVIEW OF VERTEBRATE WILD- LIFE FOR LISTING AS ENDANGERED AND THREATENED SPECIES. FED. REG. 47(251): 58454-58460.

 


 

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