An Assessment of Artificial Burrows for Burrowing Owls in Northern California

Abstract

This study assesses artificial burrows as a management tool for burrowing owls (Athene cunicularia) at two study sites in northern California. The results of t-tests showed that artificial burrows that received annual surface maintenance (n = 113) at one site were occupied for a significantly (p ≤ 0.003) greater number of years than non-maintained (n = 51) artificial burrows at the other site. Maintained burrows were occupied for a mean of 1.90 years (SD = 2.04), compared to a mean of 0.45 years (SD = 0.97) for non-maintained burrows. Even with maintenance, occupancy rates dropped from 31% during the first year to 8% during the third year post-installation. Maintenance or reinstallation of the entire burrow system appears to be crucial for longer-term use. The results of chi-squared goodness-of-fit tests showed no significant difference in nesting success (≥ 1 fledgling/pair) between natural and artificial burrows at either of the study sites (χ2 = 2.75 and 6.76, df = 3, p > 0.05). Of 120 burrowing owls raised in maintained artificial burrows, 70% were re-sighted occupying artificial burrows during subsequent breeding seasons, compared to 30% occupying natural burrows. Only 3% of these owls occupied their natal burrow during the first nesting season post-fledging. Of those owls that were re-sighted during two or more nesting seasons, almost half (48%) occupied different artificial burrows from one year to the next.