Physical footprint of oil and gas infrastructure, not anthropogenic noise, reduces nesting success of some grassland songbirds
Abstract Western North America's grasslands have undergone a rapid expansion of conventional oil and natural gas development, the effects of which are largely unknown for nesting songbirds. Understanding mechanisms that drive ecological responses to infrastructure is essential for our ability to identify and minimize potential negative effects on wildlife. Our study sought to distinguish between effects driven by physical structures and those driven by associated anthropogenic noise. Further, we evaluated whether some structure types have smaller ecological footprints than others. We monitored 747 grassland songbird nests, of five species, in Alberta's mixed-grass prairie to determine if, and why, the presence of infrastructure affects nesting success. Nesting success was significantly lower at infrastructure sites relative to controls for both Savannah sparrow ( Passerculus sandwichensis ) and vesper sparrow ( Pooecetes gramineus ), as well as at screwpump relative to pumpjack oil wells. There was no correlation between nesting success and noise intensity, and nesting success was not significantly lower near roads. However, nesting success was lower at electric grid-powered sites relative to generator-powered sites, suggesting that power distribution lines may benefit some nest predators. Vesper sparrow nest density increased with proximity to oil wells and compressor stations, so it is possible that these sites are ecological traps for this species. Management strategies focusing only on reduction of anthropogenic noise and disturbance may be ineffectual for conservation of grassland songbirds. Managers should also seek to reduce the physical footprint of infrastructure on the landscape, replace screwpumps with pumpjacks, and replace grid powered with generator-powered wells.