Mitigation translocations are increasing and if they are to fulfill their regulatory intent, the application of best‐practice principles to release strategy and monitoring is required. With an investment of 3 years, we engaged with stakeholders, including developers, to improve outcomes from mitigation translocations of an at‐risk species, the western burrowing owl Athene cunicularia hypugaea (BUOW). We evaluated the consequences of two primary translocation methods, displacement (i.e. exclusion from burrow) and translocation, against control owls, using a suite of success metrics focused on dispersal, survival and reproduction. We also tested the provision of visual and acoustic conspecific cues to dampen dispersal away from release sites. Within the displaced group, BUOW settled closer to the origin site if burrows were available nearby. Although translocated BUOW dispersed farther from the release site than displaced BUOW, this difference disappeared when conspecific cues were present. BUOW were 20 times more likely to settle at the release site when conspecifics or their cues were present. Translocating animals over longer distances (>17.5 km) reduced the incidence of BUOW returning to the origin site. When avoiding direct impacts to BUOW is not feasible, a determination of the most beneficial translocation method must be made, driven by site‐specific conditions and the feasibility of implementing best management practices. The known costs of translocation to survival may be offset by long‐term advantages such as the establishment of breeding populations inside protected areas. Mitigation translocations can benefit from carefully devised and tested hypotheses to determine what works and what does not; we advocate the increased use of evidence in mitigation translocation to guide management decisions and policies.

Obtaining reliable estimates of absolute and relative reproductive rates is challenging for avian species whose nests are difficult to observe, such as the burrowing owl (Athene cunicularia). We compared methods for estimating reproductive rates of burrowing owls, defined as the number of 21-to 28-day-old young per successful nest. We compared observations using (1) the mean and (2) the maximum number of young observed during 5 30-min observation periods, and (3) the maximum number of young videotaped during 2-hr video surveillance. We evaluated the reliability of these methods with the known number of young present in nest boxes. All 3 methods performed poorly as estimators of absolute reproductive rates (absolute bias >23%, root mean square error [RMSE] >42%). Video surveillance performed most poorly of the 3 , with a high incidence of failing to detect any young at successful nests. The maximum number of young observed from direct nest observations was correlated with the known number of young (r = 0. 82 ± 0. 13 , n = 21) and provided more reliable estimates of relative than absolute reproductive rates. The mean number of young observed from direct observations was correlated with the known number of young (r = 0. 64 ± 0. 18 , n = 21), but had both higher bias and lower precision than the maximum number observed for estimation of relative reproductive rates. Our results suggest that using counts of young observed outside of the nest burrow may lead to incorrect conclusions on factors affecting reproductive rates. When counts are the basis of inference, the effort researchers use at each nest should be standardized and reported. Further work on field methods that allow estimation of detection probability, or ensuring that all young are observed, will be imperative in providing reliable estimates.

No abstract

Studies of habitat relationships indicate that burrowing owls (Athene cunicularia) often select nest sites with multiple burrows. This behavior may increase survival of post‐emergent nestlings. We experimentally blocked access to burrows within 20 m of nests (satellite burrows) within a large grassland in central California to evaluate the response by year‐round resident burrowing owls to removal of satellite burrows. We compared reproductive performance and nest fidelity between owls whose access to potential satellite burrows was blocked and owls whose nests had similar numbers of naturally occurring burrows within 20 m of the nest prior to manipulation. Adult owls and their young moved away from treatment nests, but reproductive rates between owls from treatment and control nests did not differ. Movements involved the entire family, occurred before young had fledged, and owls did not return to the natal nest burrow. Movements ranged from 25 m to 120 m and occurred at 5 of the 7 treatment nests with young. No such movement occurred at any of the control nests. Our findings support results from correlational studies that multiple nearby burrows influence nest site selection. © 2014 The Wildlife Society