Can Restoring City Streams Bring Back Missing Birdlife?

Conservationists consider the case of the Louisiana waterthrush in Washington, D.C.鈥檚 Rock Creek Park

By Kaleb Friend
Conservation
Jun 25, 2025

A Louisiana waterthrush (above) scans for prey along a stream in Washington, D.C.’s Rock Creek Park. Efforts to restore the park’s polluted waterways include reducing stormwater runoff (below) from the surrounding city.

ON A JUNE EVENING IN 1954, Rachel Carson was hiking on a trail bathed in birdsong in Washington, D.C.’s Rock Creek Park. Her field notes from that day document her sighting of a , a sparrow-sized, brown-and-white warbler that winters in Latin 皇冠体育app官网平台 and the Caribbean, breeding and raising its young in forests across the eastern and midwestern United States.

At the time Carson recorded her notes, the waterthrush was a predictable sighting for summertime birders in woodlands adjacent to the park’s streams. But within two decades, their reports suggest that the species had stopped breeding in many parts of Rock Creek Park.

Though several factors likely contributed to this apparent decline, one clear culprit would have been the marked degradation of the 9.5 miles of Rock Creek that traverse the park. Considered a stream-dependent species, the Louisiana waterthrush needs clean running water with many kinds of macroinvertebrate prey and vertical stream banks where the bird can tuck its leafy nests into soil cavities or under exposed roots. According to research conducted in the 1990s and 2000s by Robert Mulvihill, an ornithologist for the Department of Conservation and Field Research at the , both the numbers and breeding success of the waterthrush fall with declines in water quality.

In Rock Creek Park, uncontrolled surges of contaminated stormwater runoff had been gouging out streambeds for decades, turning once lazy pools and rivulets that nurture fish and invertebrates into roaring, pollution-laced fast water with steep drops and eroded banks. As streamside vegetation declined—and both human population and impermeable pavement ballooned—the harm intensified, with each new storm turning into a filthy deluge. Periodic overflows of sewage from the city’s antiquated pipes during heavy storms added to the creek’s contamination.

Rock Creek is hardly unique. According to the U.S. Environmental Protection Agency, more than 80,000 miles of streams and rivers across the country are “impaired by urbanization.” The phenomenon is so common it’s been dubbed “urban stream syndrome.”

Urban stream degradation impacts more than wildlife like the Louisiana waterthrush. Healthy waterways help sequester carbon and retain rainfall that replenishes groundwater supplies. Intact stream banks absorb runoff of nitrogen and phosphorus, helping decrease the likelihood of oxygen-depleting algal blooms downstream. Many city streams also feed into large waterway networks critical to recreation and fisheries. The waters of Rock Creek, for example, eventually flow to the Chesapeake Bay, one of the largest U.S. fishing grounds.

Fortunately, degraded urban streams often can be restored—and Rock Creek offers a promising example of how the first steps of such an effort might unfold. In 2005, DC Water, the public utility that manages water use and disposal in Washington, D.C., initiated the , a 25-year program to reduce the volume of sewage overflows into the District’s waterways, including Rock Creek, during major storms. Ongoing efforts include construction of large sewage containment tunnels and installation of green infrastructure, such as permeable pavement and rain gardens, which help filter out pollutants. The city’s Department of Energy and Environment (DOEE), meanwhile, is strengthening stormwater runoff regulations, leading to marked and steady declines in volume and improved runoff water quality.

Other entities, including the National Park Service (NPS) and the nonprofit , have launched restoration efforts in several locations within the creek’s watershed—with a handful of projects completed to date.

Have these projects made a difference for wildlife such as the Louisiana waterthrush? Scientists often assess the success of stream restoration by analyzing water chemistry and tallying measures such as sediment load to answer the question: Has restoration recreated the hydrological, chemical and physical properties the stream originally possessed? But many biologists argue that a better way to gauge success is to find out whether a restored stream supports a wider array of life than it did before the effort.

To make such assessments, they draw on the notion of “ecological uplift,” which can be detected in part by the presence or absence of increased native species diversity within the habitat. “Uplift is an important concept in measuring restoration success and improvement from the unrestored state,” writes , an ecologist with the University of Maryland and a popularizer of the approach. But obtaining evidence of ecological uplift has remained largely elusive.

Enter the Louisiana waterthrush. Two years after NPS and DOEE collaborated in 2011 to restore a small tributary of Rock Creek known as Milkhouse Ford, summertime birders spotted waterthrushes they believed were breeding there—a location where the birds had not been documented breeding for several decades. Since then, at least four additional pairs have been sighted, along with a fledgling. Mulvihill sees these sightings as an encouraging sign that “in all likelihood does indeed reflect improvements in water quality and streamside habitat.”

is a California-based conservation photographer who concentrates on birds.