Abundant Natural Cavities in a Deciduous Forest Leads to a Lack of Nest-Box Occupancy by Northern Saw-Whet Owls
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Nest boxes are commonly used for species that utilize tree cavities, including small owls. Boxes were installed in 2011 to facilitate study of Northern Saw-whet Owls in Pennsylvania. We checked the 11 boxes that remained in 2020 after a hiatus of 8 years and found 3 rodent nests, but no evidence of owl usage. Playbacks revealed owls were present at 8 of 11 boxes checked. Cavity surveys yielded an average of 7.7 large cavities within 50 m of each box; extrapolation of cavity densities to a minimal territory size of 150 ha suggested that suitable cavities are an abundant, non-limiting resource here. Cavity abundance was likely a consequence of beech bark disease complex having recently top-killed most large American Beech trees locally, providing abundant resources for excavating woodpeckers. Assessing cavity abundance should be an essential first step for any management project involving cavity-nesting birds, and nest boxes should be used only in situations where cavities appear to be limited.
KeywordsAegolius acadicus; cavity-nester; nest box; Northern Saw-whet Owl; Pennsylvania; population regulation
Elias, Joseph M.; Stoleson, Scott H. 2021. Abundant Natural Cavities in a Deciduous Forest Leads to a Lack of Nest-Box Occupancy by Northern Saw-Whet Owls. Northeastern Naturalist. 28(2): 202-210. https://doi.org/10.1656/045.028.0209.