Influence of Environmental Conditions and Call Playback on Detection of Eastern Forest Owls During Standardized Surveys

Owls provide ecosystem services and play crucial roles in the environment making them important to monitor and study. However, standardized methods for most species do not exist, and we lack understanding of the effects of many environmental variables and playbacks on detection probability of owls. We performed a multispecies occupancy analysis on owl monitoring data collected from 2004 – 2013 across the state of Maine, to examine the effects of environmental variables, conspecific and heterospecific playback on detection, and general survey protocols for three forest owls: Northern Saw-whet Owl (Aegolius acadicus), Barred Owl (Strix varia), and Great Horned Owl (Bubo virginianus). We found that environmental variables such as cloud cover, precipitation, temperature, time of night, and wind have species-specific results, but noise resulted in decreased detection probability for all species. We did not find support for effects of snow cover or latitude on detection of any species. We also found that conspecific playback increased the detection of that species, and heterospecific playback had variable effects. Specifically, we found that Long-eared and Barred Owl playback increased the detection of Northern Saw-whet Owl, and our results suggest additional heterospecific effects may exist. Our study showed that compared to the Maine Owl Monitoring Program, surveys examining all three of our focal species can increase efficiency and lower disturbance by only broadcasting Long-eared and Barred Owl playbacks during a 10-minute survey. We recommend that future owl surveys take into account species-specific effects of conspecific and heterospecific playback, and use our results when designing survey protocols that include one or more of our focal species