Red-shouldered Hawk Habitat Model
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Draft Date:
March 2001

Species:
Red-shouldered hawk, Buteo lineatus

Use of Study Area Resources:
Reproduction throughout study area, year around use of the southern part of the study area. Red-shouldered hawks range from New Brunswick south and west across the central U.S., with a population on the Pacific coast (Crocoll 1994). They winter in the mid-eastern U.S., into Mexico.

Habitat Requirements:
Cover. Red-shouldered hawks nest in extensive, mature to old-growth woodlands, especially bottomland hardwoods, riparian areas, and flooded deciduous swamps (Stewart 1949, Crocoll 1994). They feed along the wooded margins of marshes, often close to cultivated fields and natural openings (Bednarz and Dinsmore 1981, DeGraaf and Rappole 1995). Nests of red-shouldered hawks in southwestern Quebec were located in mature, closed canopy, deciduous forest in close proximity to a natural clearing (<27 m) and to riparian or lakeshore habitat (distance to water body averaged 62 m; Armstrong and Euler 1982). Falk (1990) found associations of Connecticut nesting hawks with high beech, red maple, and hemlock densities and basal areas. Breeding habitat in Iowa was characterized as deciduous forests in the floodplain and its associated numerous small marshes and wet meadows, encompassing an area > 250 ha (Bednarz and Dinsmore 1981). Most hawk nests were along rivers and streams; the average distance to water was 142 m (Bednarz and Dinsmore 1982). Bosakowski and Smith (1997) found significant associations of red-shouldered hawk nests to distance from wetlands and distance to forest openings. Red-shouldered hawks feed on small mammals, birds, reptiles, amphibians and crayfish (Crocoll 1994).

Area. Red-shouldered hawks require large tracts of mature floodplain or riparian forests as nesting habitat (Bednarz and Dinsmore 1981); 225 ha area corresponded with 50% of maximum probability of occurrence, and 40 ha patches were the minimum used (Robbins et al. 1989). Bednarz and Dinsmore (1981) found that marsh or wet meadow feeding areas interspersed within or adjacent to the forest typically were > 22 ha, and as small as 3 ha.

Disturbance.  Effects of development on habitat value is unclear for this species.  Western birds occupy even residential areas; a high proportion of nest failures may be due to human disturbance, but the species is often tolerant of human presence (Crocoll 1994). Armstrong and Euler (1982) found more red-shouldered hawks nesting in localities without shore-front habitation; paved roads were not an apparent limitation. Bosakowski and Smith (1997) found nest sites further (mean of 890 m) than random sites (mean of 505 m) from human habitations.  

Model:
Appropriate cover types were selected (see table, below) and habitats were refined using the interspersion of open (foraging) and forested (nesting) components and habitat area. Suitable habitat complexes consisted of wetland and riparian forested covers of 40 ha or larger adjoining marsh and grasslands of 3 ha or larger.

NWI Designations (wetlands only)	Cover Types	Cover Suitability (0 - 1 scale)
	Upland deciduous forest	0.7***
	Upland coniferous forest
	Upland mixed forest	0.5***
	Grassland	0.5*
	Upland scrub/shrub
	Cultivated
	Developed
	Bare ground
PEM, L2EM	Lake/pond, emergent vegetation	1.0*
PFOcon	Palustrine forest, conifer	0.7**
PFOdec	Palustrine forest, deciduous	1.0**
PSSdec	Palustrine scrub shrub, deciduous
PSScon	Palustrine scrub shrub, conifer
PAB, L2AB	Lake/pond, aquatic vegetation
L1UB, PUB	Lake/pond, unconsolidated bottom
L2US	Lake, unconsolidated shore
L2RS	Lake, rocky shore
R1UB	Riverine subtidal unconsolidated
Rper	Riverine perennial
E1AB	Estuarine subtidal vegetated
E1UB	Estuarine subtidal unconsolidated bottom
E2AB	Estuarine intertidal algae
E2EM	Estuarine intertidal emergent
E2RS, R1RS	Estuarine, tidal river rocky shore
E2SS	Estuarine intertidal shrub
E2US	Estuarine intertidal unconsolidated shore
M1AB	Marine subtidal vegetated
M1UB	Marine subtidal unconsolidated bottom
M2AB	Marine intertidal algae
M2RS	Marine intertidal rocky shore
M2US	Marine intertidal unconsolidated shore
NOTES	* Foraging cover types ** Nesting cover types *** Nesting cover, if within 150 m of water

Model Testing: Testing was limited by the paucity of red-shouldered hawk point occurrence data. We examined the association of modeled habitat with Breeding Bird Atlas (BBA) blocks in which the species 'probably' occurred, and compared this with the occurrence of habitat in a set of randomly selected blocks. Relatively more blocks (273 of 277) in which hawks occurred had habitat, while habitat was mapped in 564 of 629 randomly selected blocks. This distribution was significantly different than would be expected by chance, indicating that the model does display areas suitable for red-shouldered hawks.

Sources:
Armstrong, E. and D. Euler. 1982. Habitat usage of two woodland Buteo species in southern Ontario. Can. Field-Nat. 97(1):200-207.

Bednarz, J.C. and J.J. Dinsmore. 1981. Status, habitat use, and management of red-shouldered hawks in Iowa. J. Wildl. Manage. 45(1):236-241.

Bednarz, J.C. and J.J. Dinsmore. 1982. Nest-sites and habitat of red-shouldered and red-tailed hawks in Iowa. Wilson Bull. 94(1):31-45.

Bosakowski, T. and D.G. Smith 1997. Distribution and species richness of a forest raptor community in relation to urbanization. J. Raptor Res. 31(1):26-33.

Crocoll, S.T. 1994. Red-shouldered hawk, Buteo lineatus. In A. Poole and F. Gill, (eds.) The Birds of North America, 107. Acad. Nat. Sci. Phil. and Amer. Ornith. Union, Washington, DC.

DeGraaf, R.M. and J.H. Rappole. 1995. Neotropical Migratory Birds: Natural History, Distribution and Population Change. Comstock Publishing Associates, Ithaca, NY. 676 pp.

Falk, J.A. 1990. Landscape level raptor habitat associations in northwest Connecticut. M.S. Thesis, Virginia Tech.

Robbins, C.S., D.K. Dawson and B.A. Dowell. 1989. Habitat area requirements of breeding forest birds of the middle Atlantic states. Wildl. Monogr. 103:1-34.

Stewart, R.E. 1949. Ecology of a nesting red-shouldered hawk population. Wilson Bull. 61(1):26-35.