The short-term impacts of logging on the jarrah forest avifauna in south-west Western Australia: implications for the design and analysis of logging experiments

Logging is a major threat to global avian diversity. If the management of logged forests is to preserve avian diversity effectively, it is critical that management decisions are driven by rigorous science. We analysed data on changes in bird density recorded during the first 12 months post-logging in an experiment designed to drive management decisions, the Kingston Block study in Western Australia, to determine whether the experiment had sufficient replication and was designed at an appropriate spatial scale to detect logging impacts. Results of a posteriori power analysis indicated that the experiment had low power, despite the number of replicates used (43) being relatively large. Given that most studies examining logging impacts have fewer replicates than this study, low power is likely to be a common issue in logging studies. A posteriori power analysis was a powerful tool in identifying which species were adequately assessed by the experiment, whereas a priori analysis was not able to identify all these species. We conclude that a posteriori power analysis should be a routine component of logging studies. We also conclude that plot-based studies, at a similar spatial scale to the Kingston experiment, are an appropriate approach to examining logging impacts on small, sedentary species, but not large, mobile species. We propose that, for this latter group, studies focusing on the ecological requirements and landscape use of specific species are likely to be the most appropriate way to examine logging impacts. Given the similarity between logging impacts recorded in this study and forest ecosystems elsewhere, we believe our findings are likely to be relevant to many forest ecosystems.