Demographic characteristics of an avian predator, Louisiana Waterthrush (Parkesia motacilla), in response to its aquatic prey in a Central Appalachian USA watershed impacted by shale gas development

Abstract

We related Louisiana Waterthrush (Parkesia motacilla) demographic response and nest survival to benthic macroinvertebrate aquatic prey and to shale gas development parameters using models that accounted for both spatial and non-spatial sources of variability in a Central Appalachian USA watershed. In 2013, aquatic prey density and pollution intolerant genera (i.e., pollution tolerance value <4) decreased statistically with increased waterthrush territory length but not in 2014 when territory densities were lower. In general, most demographic responses to aquatic prey were variable and negatively related to aquatic prey in 2013 but positively related in 2014. Competing aquatic prey covariate models to explain nest survival were not statistically significant but differed annually and in general reversed from negative to positive influence on daily survival rate. Potential hydraulic fracturing runoff decreased nest survival both years and was statistically significant in 2014. The EPA Rapid Bioassessment protocol (EPA) and Habitat Suitability Index (HSI) designed for assessing suitability requirements for waterthrush were positively linked to aquatic prey where higher scores increased aquatic prey metrics, but EPA was more strongly linked than HSI and varied annually. While potential hydraulic fracturing runoff in 2013 may have increased Ephemeroptera, Plecoptera, and Trichoptera (EPT) richness, in 2014 shale gas territory disturbance decreased EPT richness. In 2014, intolerant genera decreased at the territory and nest level with increased shale gas disturbance suggesting the potential for localized negative effects on waterthrush. Loss of food resources does not seem directly or solely responsible for demographic declines where waterthrush likely were able to meet their foraging needs. However collective evidence suggests there may be a shale gas disturbance threshold at which waterthrush respond negatively to aquatic prey community changes. Density-dependent regulation of their ability to adapt to environmental change through acquisition of additional resources may also alter demographic response.

Epigenetic response of Louisiana Waterthrush Parkesia motacilla to shale gas development

“…Although Latta et al (2015) did not trace the origin of the contaminants, the metals were hypothesized to have originated in the Marcellus Shale layer, where they are known to be abundant (Entrekin et al 2011, Chapman et al 2012). Both surface waters and benthic aquatic prey are negatively affected by shale gas disturbance at our study site (Frantz et al 2018a, 2018b). Evidence from our study suggests a strong possible link of males in shale gas disturbed areas having altered methylation (fewer methylated sites) in response to direct exposure to heavy metal contaminant sources.…”

“…We studied Waterthrush epigenetic responses during 2013–2015 as part of a 6‐year study along 14 first‐ and second‐order forested headwater stream tributaries that totalled 58.1 km at the Lewis Wetzel Wildlife Management Area (LWWMA; 39°29.654′N, 80°38.491′E) located in Wetzel County, WV, USA (Frantz et al 2018a, 2018b, 2019; Fig. 1).…”

“…As a biological indicator of biotic stream integrity (O’Connell et al 2003, Mulvihill et al 2008), Waterthrush feed primarily on benthic macroinvertebrate aquatic prey (Mattsson et al 2009) in well‐developed riffle and pool areas (Prosser & Brooks 1998). In a long‐term study, shale gas development negatively affected Waterthrush demography (Frantz et al 2018a, 2019) and its aquatic prey (Wood et al 2016, Frantz et al 2018b), but we do not know whether shale gas development may also influence Waterthrush at a physiological (e.g. Kleist et al 2018) or molecular level.…”