Owl be hard to find: Using eBird to determine the effects of urbanization on breeding great horned owls (Bubo virginianus)

Background/Question/Methods

The global urban population has increased by more than 40% since the 1900s and is expected to continue rising. Exponential urban expansion has exposed wildlife to previously unfamiliar threats such as man-made infrastructure, altered ecosystems, and homogeneous urban environments. Great horned owls (Bubo virginianus) are highly adaptable nocturnal predators with versatile diets and habitat choices. While there is a wealth of taxonomic information on B. virginianus, the effects of urban dependent factors on B. virginianus occupancy are still poorly understood. The goal of this study was to determine what effect(s), if any, 1) land use, 2) elevation, and 3) percent tree canopy cover have on B. virginianus occupancy. We used citizen science data from eBird to develop an occupancy model for B. virginianus in the Southeastern coastal plain of the United States. To reduce biases associated with using eBird, we filtered the data to account for spatial, temporal, and taxonomic bias.

Results/Conclusions

Preliminary results show a negative correlation between B. virginianus occupancy and urban land use. On the other hand, there is a strong positive correlation between B. virginianus occupancy and environments with deciduous broadleaf vegetation. Elevation seemed to have minor negative effects on B. virginianus occupancy. Determining the ecological importance of the aforementioned covariates can assist city planners in the adaptation of urban areas to better sustain a diversity of species including B. virginianus. In conclusion, this study works to not only provide a real-world application demonstrating the value of citizen science data in the creation of occupancy models, but also to fill the gaps in scientific knowledge on the effects of urbanization on B. virginianus occupancy.