Conventional oil and gas development alters forest songbird communities

Abstract

ABSTRACTEnergy extraction within forest habitat is increasing at a rapid rate throughout eastern North America from the combined presence of conventional oil and gas, shale gas, and wind energy. We examined the effects of conventional oil and gas development on forest habitat including amounts of core and edge forest, the abundance of songbird species and guilds, species diversity, and community similarity within and between mixed hardwood and oak forest types at both individual wells (local scale) and at the 25‐ha scale at differing levels of well density: reference (0 wells/site, 0 wells/km2), low (1–5 wells/site, 4–20 wells/km2), and high (10–15 wells/site, 40–60 wells/km2). Amount of cleared area, length of roads, and amount of edge increased with increasing well density, whereas amount of core forest declined. At high well densities, 85% of the study site remained forested, but the mean amount of core forest declined from 68% to 2%. Specific changes to forest structure associated with oil and gas development included decreases in basal area and canopy cover within 20 m of individual wells and with increasing well density. Of 19 species analyzed, 5 species, including ovenbird (Seiurus aurocapilla), Blackburnian warbler (Setophaga fusca), and black‐throated green warbler (Setophaga virens), had lower abundance at well sites than reference sites at either the local or 25‐ha scale. Six species including American robin (Turdus migratorius), chestnut‐sided warbler (Setophaga pensylvanica), and brown‐headed cowbird (Molothrus ater) were more abundant at well than reference sites. Eight species did not differ in abundance between well and reference sites. All 3 songbird guilds showed distinct patterns of abundance in relation to habitat differences resulting from oil and gas development that were consistent with known fragmentation effects. Forest interior species were less abundant at well sites than reference sites and showed a declining trend with increasing well density. In contrast, the guilds of early successional species and synanthropic species were more abundant at well sites than reference sites as was species richness (alpha diversity). Avian communities differed between northern hardwood and oak forest types at reference sites but became more similar when wells were present at both scales, suggesting biotic homogenization or a loss of beta diversity occurred as similar species were attracted to well sites in both forest types. The bird communities associated with northern hardwoods and oaks still retained their unique characteristics at low well densities but became similar at high well densities suggesting a threshold somewhere between the low and high well density sites. Consequently, we recommend that if well development is to occur in extensively forested landscapes, conventional oil and gas well development be limited to a maximum of 20 wells/km2 to minimize impacts to forest birds. © 2014 The Wildlife Society.