Scientific Name:
Buteo lineatus
Nest Type: Platform
Nest Location: Deciduous
trees; 10-200', avg. 20-60'
Clutch Size: 2-4;
avg. 3
Food: Small mammals,
reptiles, amphibians, birds
Foraging Guild:
Low and high patrol
The Red-shouldered Hawk
has two major populations in North America. The largest concentration
is found in forested areas of eastern North America and a smaller, disjunct
population occurs along the coast of southwestern Oregon and California
(Coffin and Pfannmuller 1988). The eastern population appears to be
expanding northward as a result of the maturing of northern hardwoods,
aspen, and mixed forest associated with streams and other wet areas
(Postupalsky 1980). In Minnesota, the Red-shouldered Hawk breeds from
Wabasha and Olmsted counties north and west to Mahnomen, Becker, and
Hubbard counties (Coffin and Pfannmuller 1988). The species is a short
to long distance migrant that winters throughout the southern portion
of its breeding range into Mexico (National Geographic Society 1983).
In Minnesota, spring migration of the Red-shouldered Hawk extends from
mid-March through early May, while fall migration occurs during early
September through early November (Janssen 1987).
The Red-shouldered Hawk
is associated with mature, open deciduous, and mixed riparian forest
habitats, with a preference for bottomlands and wooded margins near
marshes (Woodrey 1986, Bushman and Therres 1988, DeGraaf et al. 1991).
The forest is usually interspersed with small wetlands created by meandering,
flowing water (Bednarz and Dinsmore 1982).
The species nests in the
canopy of a deciduous tree, usually 12-48 in diameter (Titus and Mosher
1987), often found near water (Bushman and Therres 1988). Nests are
almost always restricted to closed forests with low conifer composition,
fewer but larger trees, a well-developed understory, a reduced subcanopy,
and low ground cover (Portnoy and Dodge 1979, Armstrong and Euler 1983).
However, it was shown in Iowa that upland forest may compensate for
limited floodplain forest at some nest sites (Bednarz and Dinsmore 1982).
Clutch size ranges from 2 to 4 eggs, usually 3 (Harrison 1975). The
species feeds on small vertebrates and invertebrates including reptiles,
amphibians, rodents, birds, and crayfish, frequently obtained from marshes
and wetlands (Ehrlich et al. 1988).
Large (250 to 625 acres)
contiguous forest tracts are necessary to sustain breeding in this species
(Bednarz and Dinsmore 1982, Coffin and Pfannmuller 1988). Finch (1991)
summarized a report by Robbins et al. (1989) and suggests that the species
is seldom present in tracts of less than 100 acres, and tracts greater
than 7500 acres may be necessary for this species. In habitats such
as fragmented, open forests, the more aggressive Red-tailed Hawk (Buteo
jamaicensis) will generally outcompete the Red-shouldered Hawk
(Campbell 1975, Bednarz and Dinsmore 1982). However, small clearings
are often utilized as hunting areas by the Red-shouldered Hawk and may
be dispersed throughout the forest (Bednarz and Dinsmore 1982). Bednarz
and Dinsmore (1982) recommended maintaining mature forest at 148 to
400 trees per acre with few understory trees.
Although the Red-shouldered
Hawk was one of many raptors adversely affected by organochlorine compounds,
nesting habitat loss and alteration is often cited as a primary cause
of the Red-shouldered Hawk's decline across eastern and central North
America (Henny et al. 1973, Bednarz and Dinsmore 1982, Armstrong and
Euler 1983). The species was listed on Audubon's Society Blue List from
1972 to 1986 because of declining numbers throughout its range (Tate
1986). Migration data collected from 1934 to 1986 at Hawk Mountain,
Pennsylvania suggest a long-term, nonsignificant decline in the species
(Bednarz et al. 1990). The Red-shouldered Hawk is currently listed as
a species of special concern in Minnesota by the Department of Natural
Resources, with a statewide breeding population estimated at less than
200 pairs in 1988 (Coffin and Pfannmuller 1988). Management practices
that disturb riverine systems, such as timber harvesting, dam construction,
and channelization may be detrimental to this species (Bednarz and Dinsmore
1981, Kimmel and Fredrickson 1981, Bushman and Therres 1988). Selective
cutting, a practice which reduces average crown diameter and lowers
tree density through the removal of the largest most mature trees, may
permit territory appropriation by the more aggressive Red-tailed Hawk
(Bryant 1986). Bryant (1986) suggested leaving a completely uncut buffer
zone around traditional Red-shouldered Hawk nest sites to discourage
Red-tailed Hawks.