Experimental reduction of a primary nest predator fails to decrease nest predation rates of sagebrush songbirds

Brewer’s Sparrow (Spizella breweri), Sagebrush Sparrow (Artemisiospiza nevadensis), and Sage Thrasher (Oreoscoptus montanus)—during May to August 2019 in western Wyoming, USA, to assess whether nest predation risk was additive or compensatory, and whether nest predator removal could comprise a potentially effective management tool. Deer mouse removal did not affect the daily nest survival of songbirds between experimental and control plots, despite a reduction of 68%–85% in deer mouse abundance within treatment areas. Therefore, nest predation in this system likely operated in a compensatory way, in which deer mice that escaped removal, new immigrants, or other species of nest predator maintained similar levels of nest predation risk regardless of the prevalence of a primary predator. We caution that predator removal may not be an effective management tool in systems that lack barriers to predator immigration or have several alternative species of predators, even when a single species typically is responsible for the majority of predation events.