This hummingbird actively defends feeding and nesting territory both inter- and intraspecifically (Cody 1968; Baltosser 1989; Calder 1993). Banding returns show the species has strong fidelity to breeding sites, wintering sites, and migration routes (Calder and Jones 1989; Calder 1993); it has been shown to have strong spatial memory for nectar sites (Hurly 1996). Rufous hummingbirds establish and defend territories around nectar sources on breeding sites, migration stopovers, and wintering sites. Migrating birds can gain an average mass of 0.23 g per day, and conserve energy by going into torpor at night (Hixon and Carpenter 1988). Feeding territory size depends on flower density and fluctuates with the rate of weight gain possible from nectar availability and the cost of territorial defense (Kodric-Brown and Brown 1978; Gass 1979; Carpenter et al. 1983). Feeding territory sizes range from 32 to 3,300 square meters (Gass 1979; Kodric-Brown and Brown 1978). Calder (1993) notes that banded birds have been recaptured at feeders 2 kilometers apart in summer.
Breeding densities reported range from 0.17 to 2.6 nests per hectare (Horvath 1964 cited in Calder 1993). In Oregon Coast Range Douglas-fir forests, densities reported at 0.16 birds per hectare in young stands, 0.13 birds per hectare mature stands, and 0.33 birds per hectare in old-growth stands (Carey et al. 1991). Average relative abundances reported on BBS routes range from 0.83 to 4.94 birds per 25-mile survey route (Sauer et al. 1997). In winter, 95 individuals captured in 12 nets over two days in a pine-oak post-fire succession habitat in Sierra de Manantlan Biosphere Reserve, Jalisco, Mexico (Calder 1993).
Baltosser (1983, cited in Miller and Gass 1985) reported high egg and nestling predation (25 percent to 58 percent) in four species of hummingbirds; however, nest predation is apparently unstudied in rufous hummingbirds. Predation on adult hummingbirds is not likely to play a large role in adult mortality (Miller and Gass 1985; Calder 1993).
Some observers suggest that artificial feeders may increase populations above natural levels by providing food beyond flowering seasons (see Calder 1993) or encouraging birds to delay migration past availability of natural foods. Feeders may also subject birds to predation, disease, or collision with windows. However none of these factors are fully studied or quantified (Calder 1993).
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