Effects of Oil Development on Grassland Songbirds and Their Avian Predators in Southeastern Saskatchewan

Abstract

The quantity and quality of Saskatchewan’s remaining grassland may be threatened by energy development such as oil extraction. Grassland songbird populations are declining and increased oil development may be contributing to their declines through habitat loss and degradation. More quantitative research is needed to inform our understanding of how grassland songbirds are affected by oil development. I examined grassland songbird abundance, vegetation structure, habitat type (native and planted grasslands), and avian predator occurrence across a gradient of oil disturbance to determine the extent to which oil well proximity, density, and cumulative habitat disturbance influences the abundance of grassland songbirds and the occurrence of avian predators. I conducted 486 point counts in 243 sample sites (259 ha) at varying distances from oil wells, and in areas with varying well densities (0-48 wells/259 ha). The abundance of seven songbird species was reduced near oil wells or in areas with higher well densities, the abundance of two species was not influenced by oil wells, and the abundance of two species increased in the presence of oil wells or with greater well density. Three species also exhibited reduced abundance with greater cumulative disturbance, while two species exhibited reduced abundance when the area covered by well pads or oil access roads increased. I also found evidence that the abundance of four species was lowest in planted grassland compared to native grassland in the presence of oil development. My results indicate that oil development influenced vegetation structure, which likely influenced grassland songbird abundance to some degree. However, structural changes in vegetation did not account for all observed variation in songbird abundance. Finally, my results provide evidence that Northern Harrier occurrence is negatively influenced by oil development but that buteos and corvids are not affected. Northern Harrier occurrence is possibly influenced by habitat fragmentation caused by oil development since they are known to be area sensitive. As oil development increases in grassland habitat, its negative impacts on grassland songbirds will likely become more pronounced. Efforts should be made to limit well density and the cumulative area of disturbance on the landscape.