Shallow gas development and grassland songbirds: The importance of perches

Abstract

Grassland bird species have declined more than birds of any other region in North America and industrial development may exert further pressure on these species. We evaluated effects of conventional natural gas infrastructure on the relative abundances of grassland songbirds in southeastern Alberta, Canada at sites with shallow gas well pad densities ranging from 0 to 16 pads/258 ha (0–24 well heads/258 ha). Conventional gas wells have a relatively small footprint and minimal associated noise and maintenance activities, allowing us to focus on effects of the infrastructure itself and vegetation surrounding wells. We conducted fixed‐radius point counts and vegetation sampling at 34 sites in 2010 and 40 sites in 2011. We used generalized linear mixed models and information theory to evaluate effects of infrastructure on birds. Relative abundances of vesper sparrow (Pooecetes gramineus) and western meadowlark (Sturnella neglecta) increased near gas wells, whereas abundance of the threatened Sprague's pipit (Anthus spragueii) declined. Vegetation near infrastructure was shorter and sparser than locations farther from wells, but discrepancies with avian habitat preferences suggest that, in contrast to conclusions of previous studies, vegetation structure could not explain responses to infrastructure by birds. Instead, gas wells may have acted as artificial shrubs because they attracted species that use vegetation for perching but were avoided by species that avoid shrubs. Our results suggest that observed effects were a direct result of the presence of wells and associated fencing, and thus risk mitigation should focus on reducing the extent of aboveground infrastructure. © 2017 The Wildlife Society.

Effects of shallow natural gas well structures and associated roads on grassland songbird reproductive success in Alberta, Canada

“…Given that neither distance to well nor well density influenced the nest success of either focal species, our results suggest that nest failure caused by the presence of shallow gas wells is small, nonexistent, or compensatory [48]. As we found no effect of distance to shallow gas wells on relative abundance of Savannah sparrows or chestnut-collared longspurs in point-counts conducted in the same study sites [39], it is unlikely these patterns resulted from individuals selecting nest sites far from infrastructure.…”

“…Despite shorter and exotic vegetation near gas wells [22, 39], these changes did not affect nest success. This suggests that sufficient vegetation remains on the landscape to allow individuals to select sites with suitable cover and protection from predators [64, 65].…”

“…Elsewhere we have shown that litter depth is shorter near newer shallow gas wells, but this effect decreases as wells age, presumably because vegetation destroyed during well construction gradually regenerates over time [22]. Short vegetation and higher abundances of exotic grasses near wells [22, 39] may lead to lower availability of invertebrates and seeds [68–70], which are primary food sources for chestnut-collared longspurs during the breeding season [71–73]. Therefore, food availability may increase as residual effects of well construction decline over time.…”

“…Although vegetation may have grown since nest sites selection, we did not measure vegetation until after the nest succeeded or failed to minimize disturbance to active nests. Our research elsewhere in Canada’s mixed-grass prairies demonstrates that vegetation structure is highly correlated within years, when measured as much as 2–3 months apart during the growing season (r = 0.684–0.831) [39] and thus it is reasonable to assume that our vegetation measurements provide a suitable index of vegetation structure during nest construction. Nonetheless, our measures of vegetation structure are relative indices of structure, rather than accurate measurements of nest site selection conditions.…”

Oil and natural gas development influence nest‐site selection and nest survival of upland‐nesting waterfowl and shorebirds

“…Oil and natural gas wells are often associated with roads and trails, which provide access for construction and maintenance, as well as exotic invasive species such as crested wheatgrass ( Agropyron cristatum ), which was formerly used for revegetation and reclamation purposes. Despite the dramatic increase in energy development, research on the effects of such activity on grassland‐breeding birds is limited and primarily focused on greater sage‐grouse ( Centrocercus urophasianus; Lyon and Anderson , Walker et al ) and songbirds (Kalyn Bogard and Davis , Ludlow et al , Rodgers and Koper ).…”