A Feathered Face of Forest Fragmentation
By Patrick McShea
Educator, Carnegie Museum of Natural History
Can a hymn-like bird song serve as a call for better regulation of Pennsylvania’s booming shale gas industry? The thought first occurred to me last summer after a unique forum at the Oakland studios of WQED, an open discussion about the opportunities and challenges of Marcellus Shale natural gas drilling. As I drove across a rutted patch of Fifth Avenue, the backseat contents shifted, triggering a recording of forest bird calls that I use in my role as a Carnegie Museum of Natural History educator. Specifically, flute-like hermit thrush notes provided a sound track completely at odds with the urban surroundings.
The story of the hermit thrush offers another perspective to the Marcellus Shale discussion.
More appropriate settings for the song that renowned naturalist John Burroughs termed “the finest sound in nature” lay miles to the east and north amid the upper reaches of hemlock-shaded hillsides flanking Laurel Ridge, and all across the vast hardwood forests of north central Pennsylvania’s high plateau. Here the hermit thrush population has been steadily increasing for five decades, a trend attributable to expanding and maturing forest cover.
Current shale gas development practices, however, threaten to dramatically reduce the populations of hermit thrushes and many other species because of forest fragmentation. The term denotes the process whereby blocks of wooded property are converted to other uses or, more subtly, are split into increasingly smaller parcels by roads, pipelines, or power lines.
This alteration of forest patterns is routinely listed among the issues related to Marcellus Shale development but seldom discussed. In hopes of remedying that, I brought a preserved, stuffed hermit thrush to the WQED forum.
Since the spring of 2011, I have been part of a small team of museum educators interacting with visitors to share information about forest fragmentation as a side effect of the natural gas rush, as well as other energy-related sources such as windmills. For example, gas development in our region involves not just the clearing of wooded acreage for well pads and water storage facilities, but also the building of access roads to and through remote sites, and the cutting and long-term maintenance of hundreds of miles of broad corridors for gas gathering and transmission pipelines.
Titled “Managing Marcellus: A Deliberate Theater Event,” the WQED gathering invited 60 participants, selected by lottery from email applicants, to give voice to their opinions and concerns after a lively theatrical performance featuring characters holding different views about the Marcellus Shale topic.
For my part, I presented the 6-inch-long bird for inspection as a feathered face of forest fragmentation, asking my tablemates to imagine themselves amid a fern-scented Laurel Highlands hollow as I played the recording of the thrush’s song. Later, when the rough road triggered the bird song in my backseat, I recalled the request of someone in my group who thought the thrush should star in a more imaginative dramatic production: “Tell that bird’s story,” he said. “More people should think about the full impact of Marcellus Shale.”
A bird’s story
In the life of a forest, separate parts do not equal a whole. Consider the story of a mating pair of hermit thrushes.
The patch of hemlock-shaded rhododendron on the forested ridge seemed in order to the male hermit thrush on the day he returned to Pennsylvania in mid-April. The brown-backed and speckled-bellied bird claimed this tiny portion of forested high ground by singing—with persistence. Within 10 days he had attracted a female to the thicket, and after nest construction she laid three eggs.
Both birds had been away from Pennsylvania since late fall, spending the coldest winter weeks in forested parts of eastern Tennessee. Like all migratory birds, their well-being depends upon a proper habitat in two geographically separate places, as well as refueling sites in between.
During the birds’ southern sojourn, energy-related development had made their Pennsylvania nesting territory the most vulnerable link in their Appalachian support network. A miles-long, razor-straight corridor the width of a highway had been cut and cleared across the ridge to hold a pipeline transporting natural gas from a dozen new deep wells due north. Although the edge of the corridor was 40 forested yards from the rotted oak stump the female chose to build her nest against, the changed landscape dramatically lowered the chances that the pair would successfully reproduce.
One damp spring dawn, during one of the female thrush’s rare feeding forays, a female brown-headed cowbird slipped quietly onto the nest, used her beak to puncture and remove one of three warm eggs, and laid a replacement. This took all of 90 seconds, but for the pair of thrushes it made futile all of their efforts—the hundreds of miles of migration and the days of nest building.
The alien egg was accepted without question by the female thrush, and owing to a schedule fine-tuned over thousands of generations, hatched two days before its step-siblings.
The thrush parents instinctively concentrated their feeding efforts on the precocious cowbird nestling, nurturing the alien to flight while their own genetic offspring perished. Nearby, the same scenario played out in scarlet tanager and black-throated blue warbler nests, negating breeding efforts commenced after respective migration flights from Brazil and Jamaica.
Over the past two centuries, the cowbird’s range has expanded eastward from the Great Plains as forests were felled to expand agriculture and the fuel industry. Increasing fragmentation of Pennsylvania woodlands will allow cowbirds and other predators to wreak ever more havoc on the hermit thrush and other deep-forest birds.
Without effective strategies to minimize the breaking apart of our country’s forests, a defining and stunningly beautiful sound of Appalachia might someday be silenced. That’s a story worth telling.
(The full version of this article first appeared in the opinion pages of the Pittsburgh Post-Gazette.)