Nest survival and productivity of translocated and resident burrowing owls in Arizona

Development activities associated with urbanization can directly displace animals, causing high mortality and dispersal rates. Wildlife managers have attempted to mitigate the impacts of development on burrowing owls (Athene cunicularia), a species susceptible to ground-disturbing activities, by translocating them away from areas slated for development. In this study, we evaluated the effects of translocation on burrowing owl reproduction by comparing nest survival and productivity of owls involved in an ongoing translocation program in Arizona, USA, with that of resident owls. We used nest survival models to evaluate differences in nest survival and generalized linear models with Poisson error to assess differences in productivity. In 2017, cumulative nest survival (CNS) was lower among current-year translocated owls (i.e., owls translocated within the last year; CNS = 0.34, 95% CI = 0.18, 0.51) compared to non-translocated resident owls (0.83, 95% CI = 0.71, 0.94), but CNS was similar between previously translocated owls (i.e., those translocated >1 yr ago, CNS = 0.81, 95% CI = 0.64, 0.98) and residents. Likewise, in 2018, CNS was lower for current-year translocated owls (CNS = 0.12, 95% CI = 0.00, 0.24) compared to residents (CNS = 0.68, 95% CI = 0.50, 0.87) and previously translocated owls (CNS = 0.65, 95% CI = 0.40, 0.90). Productivity was significantly lower for current-year translocated owls ( x = 0.5 fledglings/nest) compared to residents ( x = 2.4 fledglings/nest) and previously translocated owls ( x = 1.5 fledglings/nest) across sites and years. With the current methods of translocation, owls had poor reproductive success in the first year after release, but if they survived 2 years after release, they had similar nest survival and productivity compared to residents. Our results demonstrate that the current practice of releasing translocated burrowing owls in the Phoenix, Arizona area during the breeding season depresses reproduction and should be substantially changed. Nest survival was low and this was mainly attributed to nest establishment of translocated owls within release tents (acclimation structures used in translocations that involve soft release) where 85% of nests failed following tent removal. Translocation approaches that reflect a closer fit to the timing and behavior of the species should be tested to determine whether they result in better success. In particular, future studies should examine the translocation results of releasing owls as male-female pairs or single birds during the nonbreeding period.