Effects of Oil and Gas Development on Songbird Abundance in the Allegheny National Forest

Open Access
Author:
Thomas, Emily Hope
Graduate Program:
Wildlife and Fisheries Science
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
July 11, 2011
Committee Members:
  • Margaret Brittingham And Walter Tzilkowski, Thesis Advisor
  • Margaret Brittingham, Thesis Advisor
  • Walter Matthew Tzilkowski, Thesis Advisor
Keywords:
  • fragmentation
  • wells
  • abundance
  • songbirds
  • Pennsylvania
Abstract:
Numerous studies have examined the effects of forest fragmentation on songbird abundance and demographics citing decreased nest success from increased levels of predation and parasitism and decreased suitable habitat as possible lower abundances and reduced fecundity. Many of these studies looked at traditional forest fragmentation where patches of mature forest are isolated by surrounding agricultural or suburban development. The development of shallow oil and gas resources in the Mid-Atlantic region causes a different type of fragmentation, where small well pads and access roads perforate a mature forest landscape. I looked at the effects of shallow oil and gas development on songbird abundance at both the local scale of individual wells and the landscape scale at differing well densities. I used fixed-radius point counts to survey songbirds at both scales. At the local scale I compared active well sites and paired control sites. At the landscape scale I compared 25 hectare sites with various levels of oil and gas development: control (0 wells/site), low well density (1-5 wells/site), and high well density (10-15 wells/site). I also took vegetation measurements within each site to determine if any habitat characteristics varied with the presence of wells. Closed canopy nesters, black-throated green warblers (Dendroica virens), blackburnian warblers (Dendroica fusca), ovenbirds (Seiurus aurocapilla), and dark-eyed juncos (Junco hyemalis) were more abundant at control sites than at well sites at the local scale, and small-gap canopy nesters, understory nesters, American robins (Turdus migratorius), veerys (Catharus fuscescens), chestnut-sided warblers (Dendroica pensylvanica), and chipping sparrows (Spizella passerina) were more abundant at well sites than at control sites. At the landscape scale, cavity/snag nesters, small-gap canopy nesters, yellow-bellied sapsuckers (Sphyrapicus varius), and chipping sparrows increased with increasing well density. No nesting guild showed a negative response to wells at the landscape scale; however, red-eyed vireo (Vireo olivaceus) abundance decreased with increasing well density. Species richness was higher at well sites than at control sites and increased with increasing well density. Avian communities differed between northern hardwood and oak forest types at control sites but were not significantly different when wells were present at both the local and landscape scale. Canopy cover and basal area were lowest 20 m from well sites at the local scale and decreased with increasing well density at the landscape scale. My results suggest that shallow oil and gas development altered mature forest habitat enough to significantly affect the abundance of species in all four nesting guilds examined in this study. The development creates small-gaps, regeneration and snags along roads and well pads which benefit many species; however, closed canopy nesting species lose essential core forest habitat. Also, shallow oil and gas well development in a mature forest landscape shifted the songbird community structure from unique to more similar regardless of forest type, suggesting biotic homogenization of songbird communities in areas of shallow oil and gas well development.