Cliff-Dwelling Bird Species Show Variable Behavioral Responses to Rock Climbing

Abstract

Cliff environments have historically been relatively undisturbed, but growth in the popularity of rock climbing is changing this pattern. As land managers face increasing pressure to open new rock climbing areas, there is a need to understand the potential impacts of human presence on cliffs. To that end, we examined how rock climbing activity affects the occurrence and behavior of passerine birds, with a focus on the behaviors of four cliff-specialist bird species at high- and low-use climbing sites. We found that rock climbing use level did not affect the occurrence or behavior of white-throated swifts (Aeronautes saxatalis). Violet-green swallows (Tachycineta thalassina) showed small behavioral changes and were frequently observed at high-use climbing sites, suggesting an attraction to humans. In contrast, the behavioral patterns, but not occurrence rates, of common ravens (Corvus corax) and canyon wrens (Catherpes mexicanus) were affected by rock climbing site use. In particular, canyon wrens engaged in a greater diversity of behaviors at low-use climbing sites, with reduced foraging and singing at high-use climbing sites. Results indicate that avian species are differentially affected by rock climbing, with white-throated swifts and violet-green swallows coexisting well with climbers. Canyon wrens showed the strongest responses to rock climbing, making them a species of concern and a target for protection because they are cliff-dependent and experiencing population declines. We recommend including behavioral observations when monitoring specialist species, so that such data can inform management relating to recreation at cliff areas.