Assessing Avian Responses to Habitat Management Along Pipeline Right-of-ways in Eastern Ohio
Lewis L. Lolya, MS
Advisor: Stephen N. Matthews
Early successional bird species have exhibited population declines across North America coinciding with a loss in early successional forest habitats. Additionally, forest conversion and fragmentation has increased with the recent boom in unconventional shale gas development throughout Appalachia; a critically important region for songbird conservation. However, pipeline ROWs (right-of-ways), which represent the largest proportion of the modern shale gas development footprint, provide new opportunities for early successional habitat management. This potential has been demonstrated for similarly configured powerline ROWs managed using Integrated Vegetation Management (IVM) approaches, but minimal research is available for corridors with underground infrastructure that require more strict vegetation management regulations. To understand the potential of natural gas pipelines to harbor shrubland habitat, I investigated the application of forest edge-notch techniques and IVM treatments to pipeline ROW edges to promote increased structural complexity of vegetation and to mitigate the negative effects of high contrast edges. The goals of this study were to describe the current avian community structure at the pipeline-forest interfaces and how it compares with similar landscapes and core forest habitats. Additionally, I wanted to assess the response of early successional bird communities to edge-notch vegetation treatments that promote increased shrubland structure and edge complexity along pipeline ROWs. Finally, I aimed to estimate avian breeding parameters, including rates of nest survival, predation, and nest parasitism of early successional birds that nest along pipeline edges to assess the viability of these nesting habitats for declining species.
Forest-edge plots (control=11, experimental=12) were established at 10 sites across five counties in Eastern Ohio. Edge-notch treatments significantly decreased basal area (76%, P < 0.001), canopy cover (46%, P = < 0.001), and understory structure (66%, P = 0.003) from 2016 to after the first growing season in 2017, but shrub structural complexity increased in 2018, the second growing season post treatment. Seventy nine total avian species were observed during point counts in 2016, 2017, and 2018. Pipeline avian community composition reflected more of a shrubland generalist than a shrubland specialist community. No differences in abundance were detected for focal species or focal species guilds between control and treated ROW edge plots. Additionally, Acadian flycatcher was consistently more abundant in interior forest habitats, while abundances of other focal core forest avian species were not affected by point count location. Early successional species were positively associated with decreases in canopy cover and basal area and increases in invasive stems, while core forest species did not exhibit relationships with macrohabitat variables. A total of 95 nests of 13 species were monitored in 2017 and 2018 combined; 49% percent of all monitored nests were successful. Northern cardinal, wood thrush, eastern towhee, and all monitored species combined had Mayfield nest success estimates of 0.32, 0.28, 0.12, and 0.26 respectively. There were no differences in daily nest survival rates between treatments or nest-scale vegetation variables for any monitored species. Overall incidence of nest parasitism by brown-headed cowbird was relatively high across plots (18%) and did not differ between edge types. These results demonstrate that shrubland avian populations on pipelines are abundant, but vegetation characteristics and regulatory constraints may limit the viability of pipelines as breeding habitat for some shrubland specialists compared to powerline ROWs that can harbor greater shrubland area. Although pipeline edges may provide nesting habitat for shrubland generalists, high occurrence of nest parasitism and invasive species at my sites may indicate the presence of a habitat trap. Furthermore, as experimental cutback zones regrow, it will be essential to evaluate the long term dynamics of these habitats to evaluate their effectiveness of providing productive habitat for shrubland dependent birds. These results provide evidence that tracking abundance and productivity of birds will be essential for developing future pipeline corridor management guidelines.