Rocky Gorge Reservoir – Supplee Lane Recreation Area & Duckett Dam

Note: As of September 8, 2022, WSSC has posted a public health advisory with respect to contact with the water at Rocky Gorge Reservoir. Toxic bluc-green algae have been detected in the water, and may cause illness upon contact or ingestion. See the WSSC website for more information.

Rocky Gorge Reservoir and the T. Howard Duckett Dam are located on the Patuxent River at the juncture of Howard, Montgomery, and Prince George’s Counties. This Birder’s Guide entry covers access to the reservoir only in the Prince George’s County portion.

Duckett Dam was built in 1952, creating the Rocky Gorge drinking water reservoir that is owned by the Washington Suburban Sanitary Commission (WSSC). WSSC also owns the surrounding watershed lands, with the Prince George’s County portion amounting to about 270 acres.

Through its Watershed Recreation Users Program, WSSC provides access to the reservoir and the surrounding watershed lands. This is a relatively quiet, under-birded area, although there is often distant road noise from the nearby I-95 corridor. There are three primary access sites in Prince George’s County; the only confusing issue is that there are multiple names used on maps for each part of the watershed lands:

Birders often refer collectively to the three sites as “Rocky Gorge” or simply “Duckett” or “Supplee.” Note that the Rocky Gorge Watershed trail map from WSSC (link at left) does not have these three areas labelled, but the interactive Google map at left does have labels on these areas.

There is no public access to Duckett Dam itself, which is fenced off and not open to visitors. However, from the ballfields and open space at Panther’s Field, a birder can view the dam and waters adjacent to the dam. The main attraction here is a chance to see nesting Cliff Swallows, a hard-to-find species in Prince George’s County, as well as the possibility of finding a Common Raven nest.  Ravens first nested on a communication tower near the dam in 2010, one of the first successful expansions of ravens into this area. As of summer 2021, ravens are still in the area; the current nest location is unknown. Also check the forest edge along the playing fields here and pay particular attention to the fence line facing the reservoir, with views of the water, the dam, and the communication tower. Songbirds often perch up on the fence line.

The ballfields and community center open space at Supplee Park, just a short distance to the west on Brooklyn Bridge Road, have the usual suburban-type birds that use woodland edges, but traveling north from the park along Supplee Lane into the Supplee Lane Recreation Area on the south shore of the reservoir brings you into a good variety of habitats. Once north of the community park, Supplee Lane runs  through a rich deciduous forest with some scattered conifers and well-vegetated stream valleys. The woodlands hold a good selection of flycatchers, thrushes, vireos, warblers, and other Forest Interior Dwelling Species in season.

Supplee Lane ends in a large parking area at the shore of the reservoir, with a boat ramp and soft launch at the shore and an adjoining shady picnic grove. There is a good view of the reservoir and its shoreline, which will be more or less exposed depending on water levels. At the reservoir, look for waterfowl, herons and egrets, swallows and swifts, maybe a gull or tern.

Up to 5 miles of trails can be accessed from the parking area trailhead; if you wished, you could walk all the way into Montgomery and Howard Counties. The trails are all natural-surface and have some steep sections and wet stream crossings. There is an especially birdy area with scrub-shrub habitat at a powerline cut that lies west of the parking area and picnic grove. The powerline cut runs north-south; note that, unlike the WSSC watershed property, the powerline cut is accessible year-round and can be used to walk from Brooklyn Bridge Road nearly to the reservoir during the winter, when the watershed lands are closed to entry.

A good strategy for birding Rocky Gorge is to first check the shrubs and trees along the Supplee Park playing fields adjacent to Brooklyn Bridge Road. Then, during the March to November public access period, you can proceed up Supplee Lane on foot toward the reservoir to look for forest birds; there is often a concentration at the stream crossing. The one-way distance on Supplee Lane from Brooklyn Bridge Road to the reservoir is about 0.6 miles.

At the boat ramp, trails lead in both directions along the shoreline, providing better views of the reservoir. On the west side, the power line cut offers the best variety of birds in all seasons and connects back to Brooklyn Bridge Road (via a short trail through the forest back to Supplee Park), completing the loop.

Then drive east on Brooklyn Bridge Road to finish up with a look at the dam area from the Panther’s Field ballfields.

There are three eBird hotspots covering the area:

• Rocky Gorge Reservoir–Supplee Park (PG Co.) – 162+ species. This is the main hotspot covering the boat launch, shoreline trails, picnic grove, and the majority of Supplee Lane north of the community park. It also can be used for the portion of the reservoir waters in Prince George’s County.
• Rocky Gorge Reservoir–T. Howard Duckett Dam (PG Co.) – 128+ species. This hotspot includes the Panther’s Field/Bonds Mill Park ballfields and the southwest end of the dam in Prince George’s County.
• T. Howard Duckett Park – 31+ species, but only 4 submitted checklists. This hotspot is for the Supple Park community center area and ballfields at the south end of Supplee Lane.

Note that there are additional eBird hotspots covering sites around the reservoir in Howard and Montgomery Counties, including the far side of Duckett Dam.

Year-round: Great Blue Heron along the shore (scarcer in Winter); Black & Turkey Vulture on the powerline towers; Bald Eagle & Belted Kingfisher at the reservoir (both scarcer in summer); Pileated Woodpecker and Northern Flicker in the forest; Fish Crow flying overhead in ones or twos; Common Raven at the reservoir and especially the dam.

Early spring through late fall: Double-crested Cormorant on the reservoir; Osprey at the reservoir (usually with a nest on the communication tower); Eastern Phoebe along the powerline cut; Chipping Sparrow by the playing fields and along the powerline cut.

Summer: Yellow-billed Cuckoo, Eastern Wood-Pewee, Acadian Flycatcher, Great Crested Flycatcher, Red-eyed Vireo, Blue-gray Gnatcatcher, Wood Thrush, and Ovenbird in the forest along Supplee Lane; Eastern Kingbird, White-eyed Vireo, and Baltimore Oriole by the playing fields; Yellow-throated Vireo in the forest closest to the reservoir; Barn Swallow at the playing fields and along the shore; Cliff Swallow at the dam and adjacent playing fields; House Wren, Gray Catbird, and Brown Thrasher at woodland edges and along the powerline cut; Yellow-breasted Chat, Orchard Oriole, Common Yellowthroat, and Blue Grosbeak along the powerline cut; Pine Warbler in patches of pine forest along Supplee Lane and at the boat ramp; Scarlet Tanager in the forest or at woodland edges; Indigo Bunting by the playing fields and along the powerline cut.

Spring and fall migration: Common Loon and Red-throated Loon are possible in spring; Bonaparte’s Gull and Caspian Tern (mainly spring); Spotted Sandpiper along the shore; Blue-headed Vireo and Ruby-crowned Kinglet in the forest; Veery and Swainson’s Thrush in the forest or at woodland edges; Swamp Sparrow at the Supplee Lane stream crossing and along the powerline cut; various warblers and Rose-breasted Grosbeak at woodland edges (check the playing field edges in particular) and along the powerline cut.

Winter: Common Merganser and Ring-billed Gull on the reservoir; Yellow-bellied Sapsucker, Golden-crowned Kinglet, Brown Creeper, and Winter Wren in the forest; Red-breasted Nuthatch (irregularly) in the patches of pine forest along Supplee Lane and at the boat ramp; Hermit Thrush, Purple Finch, and Yellow-rumped Warbler in the forest or at woodland edges; Field Sparrow, Fox Sparrow, White-crowned Sparrow (irregularly), Savannah Sparrow (irregularly), and Red-winged Blackbird along the powerline cut.