Habitat use by barn owls across a rural to urban gradient and an assessment of stressors including, habitat loss, rodenticide exposure and road mortality

Abstract

Urbanization and agricultural intensification resulting in habitat loss is having a profound negative effect on grassland and farmland birds worldwide. Barn owls (Tyto furcata), as a species, have been affected by this intensification. To evaluate how urbanization and agricultural intensification affects barn owls we sought to address: 1) how human land use influences barn owl hunting behavior and diet, and 2) do habitat and prey choice influence the likelihood of barn owls consuming anticoagulant rodenticide (AR) exposed prey. We radio tagged 11 owls across the rural-urban landscape gradient in the Lower Mainland, British Columbia, and collected sufficient location data on 10barn owls. We found that the 95% kernel home-ranges ranged from 1.0 to 28.5km2 (n=10) and were positively correlated with the proportion of urban land use within home-ranges. Barn owls across all landscapes selected roadside grass verges significantly more than other habitat types within home-ranges, which may reflect the loss of grassland associated agriculture in the region. The risk of consuming AR exposed prey was highest in roadside grass verges compared to other habitat types. However, the overall likelihood of consuming AR exposed prey significantly decreased when the proportion of grass patches within home-ranges increased, which suggests smaller linear grass sections are more likely to contain AR exposed small mammal prey. These results highlight the need to retain and enhance hunting habitat for barn owls during urban development and to mitigate the risk of barn owl road mortality along major highways.