Removal of Old Nest Material Decreases Reuse of Artificial Burrows by Burrowing Owls

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Artificial burrows are considered an important management and conservation tool for burrowing owls (Athene cunicularia). This species regularly adorns natural and artificial burrows with mammal dung and other materials, which remain between years so that previous use of a nest site is often obvious. Moreover, ectoparasites (fleas) potentially overwinter in accumulated material and infest subsequent occupants. How evidence of prior use affects burrowing owl nest-site decisions is not completely understood. We examined potential effects of the presence of old nest material on reuse of nests by burrowing owls in southwestern Idaho, USA, during 2004 and 2005. We manipulated artificial burrows that owls used for nesting in the prior year by; 1) removing material from the entrance, tunnel, and nesting chamber and replacing it with fresh soil; 2) microwaving old nest material to kill ectoparasites before returning it; or 3) removing and returning material without treatment to serve as a control. Relative to removal burrows, odds of burrowing owl reuse of ‘control’ and “microwave” burrows were 3.5 and 3.8 times greater, respectively. Removing ectoparasites by microwaving did not increase odds of reuse relative to control burrows, and fleas were present on nestlings in all 3 treatment groups. Presence of old material may help owls locate specific burrows when returning from migration or may provide physiological and feeding benefits. Thus, cleaning by removal of nest material from previously used artificial burrows may be counterproductive if maximizing reuse of nest sites by burrowing owls is a management objective.