Recreation changes the use of a wild landscape by corvids

As urban areas have grown in population, use of nearby natural areas for outdoor recreation has also increased, potentially influencing bird distribution in landscapes managed for conservation. Members of the family Corvidae (crows, ravens, jays, and magpies) have strong interactions with humans and may be directly affected by recreation in wild landscapes. In Mount Rainier National Park, we evaluated the effects of vegetation, visitor use, and the availability of human-subsidized food on the use of landscape features by 4 corvid species: Steller's Jay (Cyanocitta stelleri), Gray Jay (Perisoreus canadensis), Common Raven (Corvus corax), and Clark's Nutcracker (Nucifraga columbiana). We conducted >1,400 point counts across areas that varied in habitat and in the degree of human recreational impact. We calculated predicted occupancy values while allowing for variation in detection probability. In addition to species-specific suites of vegetation and landscape variables, we found that patterns of human recreation, such as visitor use, food subsidy, and amount of road edge, were also significant in explaining corvid distribution. The number of visitors present during point counts was positively associated with Steller's Jay and Clark's Nutcracker use. Common Ravens used areas with fewer people but with a high density of road edge. Gray Jays, Common Ravens, and Clark's Nutcrackers were each more likely to use sites with anthropogenic food subsidy than sites without subsidies. These changes in landscape use may affect the performance of ecosystem services by corvids and could serve as useful and easily measured bioindicators of the impacts of recreation.