Weak support for cumulative effects of industrial disturbance on three owl species in Alberta’s boreal forest

Abstract

. Human-caused disturbances are encroaching on natural areas and quantifying the relative effects of different types of disturbance, and whether they interact on a landscape to create additive or synergistic cumulative effects, will provide a better understanding of how wildlife are affected. We evaluated potential cumulative effects of industrial disturbance on habitat use of Barred Owls ( Strix varia ), Great Horned Owls ( Bubo virginianus ), and Boreal Owls ( Aegolius funereus ) in Alberta’s boreal forest using acoustic survey presence/absence data and boosted regression tree analysis to quantify the relative importance and interactions of different types of industrial disturbance, as well as forest age and composition. Barred Owls were more likely to be found in older mixedwood and deciduous forest, and we found evidence suggestive of cumulative effects from a negative effect of total human footprint on habitat use and an additional negative effect of roads. Great Horned Owls were found in older forest but were relatively tolerant of disturbance, and soft linear features (seismic lines, pipelines, transmission lines) had a positive effect on habitat use, possibly due to these types of disturbances creating suitable hunting habitat. Boreal Owls were more likely to be found in older coniferous forest, and the effects of disturbance did not show clear evidence of sensitivity or tolerance to human disturbance. Our results indicate the importance of forest age and composition on habitat use for these owls. Cumulative effects varied among owl species and were potentially more significant for Barred Owl; for the other two species the effects of industrial disturbance were relatively small and there was no evidence of cumulative effects. Our study also demonstrates that assessing cumulative effects of human disturbance on wildlife using boosted-regression trees can effectively help focus conservation efforts and can be used, for example, for evaluating the environment effects of new projects prior to their implementation