Appendix B. Additional information on the occurrence functions used to buffer anthropogenic features for the corvid and domestic predator presence risk models.
Corvid presence risk model
We buffered anthropogenic resources (n = 6) using a probability function derived from daily movement patterns of American Crows (Corvus brachyrhynchos) and Common Ravens (C. corax) (Fig. 1). Average daily excursive forays between food sources and roost sites for non-breeding Common Ravens ranged from 6.9 km in Idaho (maximum distance 62.5 km) to 27 km in Michigan (range 0.8–147 km) (Boarman and Heinrich 1999). In contrast, Common Raven breeding pairs searched for food on average 0.57–0.71 km (SE) from the nest (Boarman and Heinrich 1999); this distance was smaller for American Crows (0.38 ± 0.32 km [SD], range 0.016–2.08 km [Sullivan and Dinsmore 1992]) but breeding pairs have been observed to fly >10 km from the nesting territory to anthropogenic food sources (Neatherlin 2002). There were no data available on daily movement patterns for the Black-billed Magpies (Trost 1999).
|FIG. B1. Corvid occurrence probabilities function in relation to anthropogenic features.|
Domestic cat and dog presence risk models
We modeled decay functions for domestic cats and dogs approximating the study by Odell and Knight (2001). We adjusted model to fit the 90-m resolution of the spatial data sets.
|FIG. B2. Domestic predator occurrence probabilities functions in relation to anthropogenic features.|
Boarman, W. I., and B. Heinrich. 1999. Common raven (Corvus corax). Pages 1–31 in A. Poole, and F. Gill, editors. The birds of North America, No. 476. The Birds of North America, Philadelphia, Pennsylvania, USA.
Neatherlin, E. A. 2002. Corvid Response to human settlement and recreation with implications for marbled murrelets. M.S. Thesis, University of Washington, Seattle, Washington, USA.
Odell, E. A., and R. L. Knight. 2001. Songbird and medium-sized mammal communities associated with exurban development in Pitkin County, Colorado. Conservation Biology 15:1143–1150.
Sullivan, B. D., and J. J. Dinsmore. 1992. Home range and foraging habitat of American crows, Corvus brachyrhynchos, in a waterfowl breeding area in Manitoba. Canadian Field-Naturalist 106:181–184.
Trost, C. H. 1999. Black-billed magpie (Pica hudsonia). In A. Poole, and F. Gill, editors. The birds of North America, No. 389. The Birds of North America, Philadelphia, Pennsylvania, USA.