A 23-Year Study of Bird Populations Near Sandstone Falls

A researcher holds a hooded warbler.

NPS photo

Bird watching is an activity that many visitors enjoy in New River Gorge National Park and Preserve (NERI). This park is located in the central Appalachian mou­ntains, an area rich with important habitats and breeding grounds for neotropical migratory birds. Not only is birding a fun form of recreation, bird monitoring also tells us about the environment and how it changes over time. NERI is a participant in a long-term, nationwide bird population and habitat quality survey program called MAPS, monitoring avian productivity and survivorship. Survey results, such as population changes, for species like eastern towhee, hooded warbler, Louisiana waterthrush, and worm-eating warbler are a troubling indicator for conservationists. When species like American redstart, Carolina wren, northern cardinal, song sparrow, and wood thrush are abundant, this reveals other elements to the health of the natural community.

 

A researcher bands a northern cardinal.

NPS photo

History of the Study Site

Human and climatic factors have impacted the study site. Historically, catastrophic floods occurred along the New River, scouring the riverbanks of sediment and vegetation. This allowed for a globally rare ecosystem to thrive - the Appalachian Flatrock Community. Due to the construction of the Bluestone Dam in 1949, this periodic flooding no longer occurs. Sedimentary buildup has led to an increase in invasive plant species which impact this ecosystem, increasing the threats to this community. The consequences of such changes in hydrologic cycles and the impact of invasive plant species on bird populations is being studied to this day.

The Survey Process

NERI’s MAPS station is located near Sandstone Falls. Established in 1996, this survey station is in a riparian forest next to the New River. The purpose of this study is to monitor, research, and manage nearly 150 bird species by assessing the natural bird community. Within the ~18.5 acres study area, four forest types (guilds) were found: shrubland, interior-edge, forest interior, and generalist. Species richness is studied, looking at the number of different species in an area; the more variety of species found, the higher the richness. Eight surveys are conducted each year. Fine nets are used to temporarily capture birds to determine changes in body weight, rate of capture, and species richness. Nets are checked every 20-30 minutes to reduce the amount of stress captured birds experience. Birds are then identified by species, age and weight, and banded so they can be recorded if recaptured.

 

Researchers banding birds,

NPS photo

Survey Results

Scientists have pieced together MAPS survey data, gaining a better understanding of the health of this bird community. When comparing trends in adults and juveniles, the adult population significantly decreased across all species combined, while juveniles are making up a greater proportion of the population at the MAPS station over time. The likelihood that an individual captured in any given year will survive to the next year was highest in northern cardinals and American redstarts, and lowest in song sparrows and wood thrush. Adult body weights of all species increased over the study period, except for worm-eating warblers. Three species of conservation concern, hooded warbler, Louisiana waterthrush, and wood thrush, increased over the study period, a possible indicator that conditions at the site are improving for these species. However, total captures have been considerably lower in the past five years than the average capture rate of earlier survey years.

When looking at species richness of the shrubland habitat, scientists found bird species significantly decreased over the course of the study. Interior-edge, forest interior and generalist guilds did not change. The decrease in the shrubland habitat is likely due to the changes in ground vegetation cover caused by the loss of catastrophic flooding. However, this theory is not definitive. The only species that relies solely on a riparian environment, Louisiana waterthrush, did not seem to be negatively impacted by encroaching invasive species. While invasive plant species provide birds with food resources and abundant cover, they alter ecosystem function and act as an ecological trap (poor-quality habitat).

 

For the Future

New River Gorge National Park and Preserve is home to globally significant ecosystems where science is always happening. This is an ongoing study in bird conservation and population monitoring. Birds are an important indicator of healthy or unhealthy environments, and monitoring changes in populations and diversity informs conservationists’ actions. Birds are an integral participant in natural ecosystems by assisting in plant propagation through seed dispersal, by eating pest insects, and serve as prey to other members of the environment. Further study is required to understand the effects of invasive species on avian communities, as well as to monitor efforts of conservation of the Appalachian Flatrock Community.

Works Cited

Margenau, E. L., & Paul, L. E. (2021). A 23-Year Summary of a Monitoring Avian Productivity and Survivorship (MAPS) Bird Banding Site in New River Gorge National River, West Viriginia. Retrieved from https://irma.nps.gov/DataStore/Reference/Profile/2287051

Link to the published report: DataStore - Published Report - (Code: 2287051) (nps.gov)