Fragmented Forests

Conventional oil and gas development in northern Pennsylvania altered bird communities, and the current massive build-out of shale-gas infrastructure may accelerate these changes, according to researchers in the college.

The Commonwealth’s northern tier—one of the largest blocks of eastern deciduous forest in the entire Appalachian region—is an important breeding area for neotropical migrant songbirds. These diminutive, insect-eating creatures, which breed in Pennsylvania and winter in Central and South America, contribute greatly to the health of forests.

But they are being negatively affected in areas where there are high densities of shallow oil and gas wells, says Margaret Brittingham, professor of wildlife resources who conducted a study of bird communities in the Allegheny National Forest.

The national forest, on the extensively forested Allegheny Plateau in northwestern Pennsylvania, has more than 14,000 active oil and gas wells. Although the footprint of a shallow well is much smaller than the immense Marcellus shale well pads now being built across the region, clusters of shallow wells, service roads, pads, and pipelines create networks of disturbances that fragment forests, changing songbird communities, Brittingham explained.

“The cumulative effect of many small-scale disturbances within the forest is resulting in the homogenization of bird communities, with species that inhabit the interior forest, such as black-throated blue warblers, ovenbirds, and Blackburnian warblers, being pushed out, and species that prefer living in edge habitat and near people and development, such as robins, blue jays, and mourning doves, moving in,” she said.

Brittingham noted that the generalist bird species that do better around people and tend to be common wherever there are people or development were more abundant near oil and gas development than within undisturbed forest—potentially displacing the forest specialists.

“Our results revealed changes in avian guilds resulting from oil and gas development and suggest that a loss of community uniqueness is a consequence.”

The paper—which also included author Emily Thomas, instructor in the wildlife technology program at Penn State DuBois—was published in a recent issue of the Journal of Wildlife Management.

Brittingham and her students are currently studying the effects of shale-gas development on birds to determine how it affects avian communities.

—Jeff Mulhollem