Red-shouldered Hawk (Buteo Lineatus)
- Assessment Summary
- Executive Summary
- COSEWIC History, Mandate, Membership and Definitions
- Lists of Figures and Tables
- Species Information
- Population Sizes and Trends
- Limiting Factors and Threats
- Special Significance of the Species
- Existing Protection or Other Status Designations
- Technical Summary
- Acknowledgements and Authorities Contacted
- Information Sources and Biographical Summary of the Report Writer
The Red-shouldered Hawk breeds in a variety of forest types, including bottomland hardwood, riparian areas, flooded deciduous swamps and upland mixed deciduous-coniferous forest. Nearby wetlands or other aquatic areas are essential. Red-shouldered Hawks do not readily use upland forests except in areas immediately adjacent to bottomland or riparian habitat (Bednarz and Dinsmore 1981; Howell and Chapman 1997) or ponds and wetlands (Szuba and Norman 1989). This species is area sensitive, and prefers extensive forest stands consisting of mature to old-growth canopy trees with variable amounts of understory (Crocoll 1994). Canopy closure appears to be a critical nest site characteristic (Jacobs and Jacobs 2002). Forest stands with the appropriate species composition, age and density are typically at least 10 ha within a mature forest that is at least 100 ha (Naylor and Szuba 1992). Although this species has been found in woodlots as small as four ha in Ontario (Campbell 1975), it is typically found in forests that are considerably larger (Bryant 1986; Naylor and Szuba 1992). Some pairs may persist at sites that have become unsuitable for a number of years because of high levels of mate and site fidelity (Bryant 1986).
Red-shouldered Hawk nests in Ontario are typically found in stands with a high percentage of sugar maple (Acer saccharum), yellow birch (Betula lutea), or other hardwoods such as American beech (Fagus grandifolia), red maple (A. rubrum), and red oak (Quercus rubra). Older (at least 60 years old) stands are preferred and canopy closure must be greater than 70%. Optimal nesting habitat also has a total basal area of at least 20 m2/ha and at least 5 m2 of this contains trees greater than 40 cm dbh (Naylor and Szuba 1992). Because of the dependence of Red-shouldered Hawks on wetlands for foraging, most nests are located within 250 m of a water body.
Large, contiguous forest tracts are necessary to sustain breeding populations of Red-shouldered Hawks. A study in Quebec found that the average home range size was 91.2 ha according to the harmonic mean and 122.9 according to the convex polygon mean (Nature-Action Quebec 1999).
The total amount and distribution of preferred habitat of the Red-shouldered Hawk in North America has declined drastically in the last 200 years. Originally, the hardwood forests that covered most of eastern North America, including southern Ontario, were composed of the wet beech-oak-hemlock and maple floodplain forest favoured by the Red-shouldered Hawk. As a result of the colonization of North America, the forests were gradually cut or cleared, and the quantity of forested habitat decreased. The overall quality of habitat also deteriorated as areas were drained or selectively logged. On average, townships in southern Ontario (south of the Canadian Shield) contained only 24% forest cover by the 1950s, and many townships in southwestern Ontario contained only 8% cover (Ontario Department of Lands and Forests 1957). Despite this extensive change, the Red-shouldered Hawk was still found nesting, even in areas with only 11% and 16% cover (Ontario Department of Lands and Forests 1957; Caster and Perks 1961). It is not known, however, whether these breeding attempts were successful.
During the 1950s, the loss of forest habitat began to slow because of forest regeneration on abandoned farmland. Presently, there seems to be sufficient habitat available in eastern and central Ontario to maintain the species. However, many of the counties south of the Canadian Shield have less than 25% forest cover, and most have far less than that. Historically, loss of forest to farmland in southwestern Ontario has had a large negative impact on the Red-shouldered Hawk and loss and fragmentation of habitat in this region are ongoing concerns. Open canopy and fragmentation of contiguous forest has created habitat that is more suitable to the larger and more aggressive Great Horned Owl (Bubo virginianus) and Red-tailed Hawk (the Red-shouldered Hawk’s closest competitor; Bednarz and Dinsmore 1981).
In other regions, cottage development may reduce breeding habitat for Red- shouldered Hawks (Armstrong and Euler 1983), although there have been observations of birds nesting within sight of cottages in some areas (Brian Naylor pers. comm.). Few Red-shouldered Hawks now breed southwest of Toronto (2nd Ontario Breeding Bird Atlas unpublished data). In Quebec, there appears to be sufficient habitat available; however, forest fragmentation is a concern throughout the Quebec range as forests continue to be lost to logging, conversion for agriculture and urban sprawl. There is insufficient quantitative information on the impacts of habitat loss on populations (Crocoll 1994).
The Red-shouldered Hawk occurs on both private and public land; however, there is little available information on the distribution of the species according to ownership. In New Brunswick, it appears that the Red-shouldered Hawk is found on private land more often than on public land (Hart 2004), and the same appears to be true for Quebec (F. Shaffer pers. comm.). There are 29 Aboriginal Lands in Ontario and Quebec within the Red-shouldered Hawk’s breeding range, but it is not known which are occupied by the species. The Red-shouldered Hawk is known to occur in several National Parks or National Historic Sites throughout its range, including: Bruce Peninsula National Park (ON), Cap Tourmente National Wildlife Area, Gatineau Park (QC), Georgian Bay Islands National Park (ON), La Mauricie National Park (QC), Lac Saint-François National Wildlife Area (QC), National Defence shooting range in Saint-Bruno (QC), Rideau Canal (ON), St. Lawrence Islands National Park (ON), Trent Severn Waterway (ON). In Ontario, breeding has been confirmed in the following provincial parks: Algonquin, Bon Echo, Charleston Lake, Inverhuron, Peter’s Woods, Frontenac, Kawartha Highlands Signature Site, Murphy's Point, MacGregor Point, Silent Lake, Fitzroy, Smokey Head-White Bluff and Killbear. Also in Ontario, nests on Crown land receive protection during the Forest Management Planning Process using spatial and temporal buffers. In Quebec, Red-shouldered Hawks occur in the following provincial parks: les parcs de Frontenac, duMont-Orford, du Mont Saint-Bruno, d'Oka, de Yamaska, de Mont-Tremblant.
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