Effects of conventional oil wells on grassland songbird abundance are caused by presence of infrastructure, not noise

Understanding the mechanisms that explain why oil infrastructure has an effect on wildlife, and comparing effects of different types of infrastructure, is necessary for determining how we may minimize or mitigate those effects. We compared the abundances of five grassland songbird species at oil well sites with different pump mechanisms and power sources, and determined the effects of exotic vegetation, perch sites, and road densities. We compared effects of wells that were active with effects of wells that were turned off to evaluate whether effects of wells were caused by noise or human activity at wells. We conducted 800-m abundance transects at 42 sites twice per year in 2013 and 2014 in Alberta, Canada. Two species at risk, Baird's sparrows (Ammodramus bairdii) and Sprague's pipits (Anthus spragueii), had significantly lower abundances at all sites that contained oil infrastructure. However, there was little evidence that noise, human activity, or traffic explained these effects. Effects of active and inactive wells were the same, and grid-powered wells had a greater effect than did generator-powered wells, although generator-powered wells are louder. Our research suggests that reducing noise, human activity or traffic would not reduce the effects of wells on grassland songbirds, and, therefore, mitigation must focus on minimizing the extent of above-ground infrastructure.