Louisiana Waterthrush Study Published


New study uses songbird as bioindicator of potential impacts of hydraulic fracturing

September 11, 2015 (Pittsburgh, PA) – Since the days when canaries were used in coal mines to warn workers of dangerous fumes, to the observations of Rachel Carson in identifying the role of pesticides in raptor population declines, birds are known to be valuable indicators of changes in our natural environment.

Building upon research begun in 1996, The National Aviary’s Department of Conservation and Field Research has been studying for 8 years the Louisiana Waterthrush as an indicator species for the health of Pennsylvania’s watersheds. Previous research showed the waterthrush as a reliable bioindicator of acid deposition, with waterthrushes consistently exhibiting lower breeding densities, altered foraging ecology, and reduced productivity on acid-polluted streams.

Based on this proven sensitivity to water quality, the Pennsylvania Game Commission formally recognized the Louisiana Waterthrush as a “Species of Greatest Conservation Need” in its Wildlife Action Plan, and as an indicator of high quality forested headwaters in the state.  Similarly, the National Park Service employed the waterthrush as a “Vital Sign” of stream ecosystem integrity across its entire Eastern Rivers and Mountain Network. 

Once the waterthrush was established as a bioindicator of the health of riparian ecosystems, National Aviary researchers recognized that as a top predator, the waterthrush would be an excellent sentinel species in the riparian ecosystem.

Now, in a new study led by Steven Latta, Ph.D. and published today in Ecosphere, the online journal of the Ecological Society of America, the Louisiana Waterthrush is used to better understand whether there may be a risk of contamination of surface waters and food webs from hydraulic fracturing activities.

For this study feathers were collected from birds inhabiting more than two dozen streams in three different states overlying the Marcellus Shale and the Fayetteville Shale regions. These feathers were analyzed for concentrations of barium and strontium, two metals that are not harmful to humans but can act as markers because they are elements that occur naturally and abundantly in the shale layer but are not common in surface waters.

Analysis of our feather samples show that in watersheds where hydraulic fracturing occurs, this obligate riparian songbird accumulates these metals associated with the fracking process. In both the Marcellus and Fayetteville shale regions, barium and strontium were found at statistically significant higher levels in feathers of birds in sites with fracking activity than at sites without fracking.

The question of what pathway these metals followed from the shale layers to enter the food chain was not examined by this study. Our data suggest, however, a recent origin for these metals in the riparian systems we studied; levels of barium and strontium in feather samples from reference sites in the Marcellus Region without fracking activity did not differ from historical samples of waterthrush feathers from the 1990s gathered prior to any fracking in the region.

Our finding of similarly elevated levels of metals associated with fracking in two geographically distant shale formations suggests hydraulic fracturing may be affecting surface waters, and underscores the need for additional monitoring and study to further assess whether any ecological or human health risks are posed by the increasingly widespread development of unconventional sources of natural gas around the world. Our study was limited to the base line analysis described above, and extensive further testing and analysis would be required to determine the levels, if any, of any dangerous substances in the watershed.

As human populations increase, our demand for natural resources also increases, and it is important to explore alternate energy resources.

“Water quality and energy development increasingly are critical issues to people across Pennsylvania, the U.S. and the world,” says Latta. “Understanding the environmental impacts of energy development and the impact of development and land use decisions on water quality in particular, are absolutely needed. My hope is that the Louisiana Waterthrush will be understood as a biological ‘canary in the coal mine.’”

 Funding for this study was provided primarily by The Heinz Endowments.


Robin Weber
National Aviary Director of Marketing & Communications
Office: 412-258-9435