Landscape characteristics and livestock presence influence common ravens: relevance to greater sage‐grouse conservation
2016
Coates, Peter S. | Brussee, Brianne E. | Howe, Kristy B. | Gustafson, Kit Benjamin | Casazza, Michael L. | Delehanty, David J.
Common raven (Corvus corax; hereafter, raven) population abundance in the sagebrush steppe of the American West has increased threefold during the previous four decades, largely as a result of unintended resource subsidies from human land‐use practices. This is concerning because ravens frequently depredate nests of species of conservation concern, such as greater sage‐grouse (Centrocercus urophasianus; hereafter, sage‐grouse). Grazing by livestock in sagebrush ecosystems is common practice on most public lands, but associations between livestock and ravens are poorly understood. The primary objective of this study was to identify the effects of livestock on raven occurrence while accounting for landscape characteristics within human‐altered sagebrush steppe habitat, particularly in areas occupied by breeding sage‐grouse. Using data from southeastern Idaho collected during spring and summer across 3 yr, we modeled raven occurrence as a function of the presence of livestock while accounting for multiple landscape covariates, including land cover features, topographical features, and proximity to sage‐grouse lek sites (breeding grounds), as well as site‐level anthropogenic features. While accounting for landscape characteristics, we found that the odds of raven occurrence increased 45.8% in areas where livestock were present. In addition, ravens selected areas near sage‐grouse leks, with the odds of occurrence decreasing 8.9% for every 1‐km distance, increase away from the lek. We did not find an association between livestock use and distance to lek. We also found that ravens selected sites with relatively lower elevation containing increased amounts of cropland, wet meadow, and urbanization. Limiting raven access to key anthropogenic subsidies and spatially segregating livestock from sage‐grouse breeding areas would likely reduce exposure of predatory ravens to sage‐grouse nests and chicks.
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