Buteo lineatus (Gmelin, 1788)
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Basis for Listing
The red-shouldered hawk has two major, but disjunct, populations in North America. The larger population ranges throughout the eastern United States and portions of Canada into the eastern Great Plains. A smaller population occurs along the Pacific coast of southwestern Oregon and California. Migratory counts suggest a slow decline in the number of red-shouldered hawks in the north-central United States. In Minnesota, the red-shouldered hawk has never been very common, and nesting in the state was not documented until 1935.
The red-shouldered hawk is a medium-sized buteo with relatively long wings. The rufous shoulder patches, which give the species its name, are diagnostic when visible, but only present in adults. In flight, the red-shouldered hawk is best distinguished by its black-and-white checkered flight feathers and the whitish crescent at the base of the primaries. The adult's underparts and wing linings are extensively barred with rufous. The red-shouldered hawk's tail has alternating black and white bands, in which the white bands are narrower than the black. This feature distinguishes it from the the similar broad-winged hawk (Buteo platypterus), which has white tail bands that are wider and fewer in number. Immature red-shouldered hawks are very difficult to distinguish from immature broad-winged hawks.
Red-shouldered hawks are most commonly found in large tracts of mature deciduous forest with scattered wetland openings. Suitable habitat typically occurs in uplands with diverse topography characterized by numerous small hills, ridges, and depressional wetlands or small lakes. Red-shouldered hawks also frequent mature floodplain forests. Researchers have found that nesting sites include high, thick canopies and trees with large diameters (McLeod and Andersen 1996). Bosakowski and Smith (1997) found that the number of red-shouldered hawks increased with increasing size of wilderness areas.
Biology / Life History
Red-shouldered hawks overwinter in lowland areas near water in the central and southern United States and Central America. They nest halfway up tall trees, well below the canopy. Nest sites are often re-used in subsequent years. Both sexes help with nest refurbishment or construction, and the female does most of the incubation. Eggs are incubated as soon as they are laid, rather than after the 4-egg clutch is complete, so young hatch asynchronously. Because the female spends much of her time brooding the young, the male does all of the hunting and brings food for both the female and the young to the nest. The young fledge at about 6 weeks of age, are able to hunt by 13 weeks, and become independent by 16 weeks. Red-shouldered hawks defend territories of approximately 200 ha (494 ac.), and they are quite aggressive towards invading owls and other hawks. The species hunts primarily during the day, usually from a perch in the forest canopy. Small mammals, birds, reptiles, amphibians, and crayfish are the most common food items taken (Crocoll 1994).
Conservation / Management
Retaining large amounts of mature deciduous forest and limiting the amount of non-forest are both important in promoting nesting and occupancy by red-shouldered hawks in central Minnesota. Land managers hoping to promote occupancy by red-shouldered hawks should avoid creating large clear-cut areas and instead use management practices that preserve the characteristics of forested landscapes (e.g., thinning and light-selection cuts). Within forested landscapes, there may be potential for small areas of intense timber harvest, as long as sufficient amounts of mature forest (>50% of the landscape), particularly hardwoods, remain (Moorman and Chapman 1996; Henneman 2006). Forest cover of sufficient maturity and extent must be maintained in close proximity to wetland openings if red-shouldered hawks are to persist in an area. Canopy closure also appears to be a critical nest-site characteristic, and some studies recommend maintaining a canopy closure of >70% for nesting habitat (summarized in Jacobs and Jacobs 2002).
Conservation Efforts in Minnesota
Extensive surveys for red-shouldered hawks have been conducted in Minnesota since the late 1980s. A large part of this effort has been the result of the Minnesota Biological Survey (MBS), which began red-shouldered hawk surveys in 1988 and has continued from 1990 to the present. In addition to MBS efforts, surveys and research projects by the Nongame Wildlife Program, University of Minnesota, U.S. Forest Service, Department of Military Affairs - Camp Ripley Environmental Office, and others have greatly expanded knowledge of red-shouldered hawk distribution, population size, and habitat use in Minnesota. Several large red-shouldered hawk concentrations have been identified, the largest of which occurs on the Camp Ripley Military Reservation and adjoining areas in central Minnesota. This concentration has been the focus of much research, and management guidelines for this site specifically, and for suitable forest sites in general, have been developed (Perry 1996).