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Red-shouldered Hawk (Buteo Lineatus)

Limiting Factors and Threats

Habitat Loss and Alteration

The most serious threats facing Red-shouldered Hawks in the southern portion of their Canadian range (i.e. south of the Canadian Shield) include habitat loss, and fragmentation or degradation of favoured deciduous forest breeding areas and wetland feeding areas (Helferty et al. 2002). Loss of wetland habitats also negatively affects this species through the disappearance of preferred prey (i.e. amphibians, snakes). Campbell (1975) suggested that Red-shouldered Hawk pairs with lower access to reptile or amphibians might have lower reproductive success.

Because Red-shouldered Hawks use extensive, contiguous mature forests, logging practices have the potential to negatively impact this species. Nesting areas that have undergone heavy partial harvests have lower rates of activity than those without harvesting or light selection cuts (Bryant 1986; Naylor et al. 2004). Selective thinning of forests in Wisconsin has resulted in an increase in Great Horned Owls and a reduction in Red-shouldered Hawks (J. Jacobs in Crocoll 1994). However, potential negative effects can be mitigated through the application of guidelines (which are applied in central Ontario) that prohibit heavy cuts within 300 m of nests and retain more than 20 ha of appropriate habitat (Naylor et al. 2004).

Loss and degradation of habitat also has indirect effects on this species. For example, incursions and replacements by Red-tailed Hawks have been strongly associated with reductions in mean tree density and tree-crown diameter from selective cutting of woodlots (Bryant 1986), and other changes in woodlot size and structure (Craighead and Craighead 1956; Postupalsky 1989).  Habitat loss and fragmentation have been and will likely continue to be most severe in the most southern portions of its Canadian range.

 

Competitive Interactions

Red-shouldered Hawks may be displaced from their nesting locations by Red-tailed Hawks and Great Horned Owls (Bent 1937; Hanna 1973; Campbell 1975).

 

Disturbance

Many Red-shouldered Hawks will avoid areas of human use (Helferty et al. 2002). For example, human disturbance (from ATVs, horseback riders, joggers, turkey hunters, campers, etc.) has pushed this species into the more remote wilderness areas remaining in the Pequannock watershed of northern New Jersey (Bosakowski and Smith 1989). In some areas, however, they are considered a suburban bird (Dykstra et al. 2001).

 

Contaminants

In the past, several toxic chemicals and insecticides have been found in Red-shouldered Hawk tissues and eggs (e.g. DDE, DDT, mercury, PCBs, dieldrin, heptachlor epoxide; Hanna 1973) and have been implicated in egg shell thinning (Campbell 1975). Because of the reduction of these compounds in aquatic ecosystems, it is likely that contaminants are not a major threat to this species. There is no available information, however, to support or refute this hypothesis.