One of the highlights of birding for me in Virginia has been Beaverdam Creek Reservoir in Loudoun County. During innumerable lunchtime visits, I have found woodlands solitude, a deserted lakeshore and a number of lifelist birds, including a Great Cormorant, Tundra Swans, Red-breasted Nuthatches, and a Pied-billed Grebe.
Located roughly between Route 7 to the north, Ryan Road to the south, Belmont Ridge Road to the east and Evergreen Mills Road to the west, the reservoir covers 275 acres and holds 1.3 billion gallons of water. There are three public access points. From the east, on Belmont Ridge Road, you can use either the Mt. Hope Road landing (by the church), or the Alford Road landing. From the west side, you can take Reservoir Road, off of Evergreen Mills Road.
Mt. Hope Road brings you the closest to the water of the three, so it also tends to have the most visitors. Trails lead off to either side from the landing.
Alford Road has the longest walk to the water. However, the path is a gravel road (blocked to traffic) that has many opportunities for woods birding. Species seen include Hermit Thrush, Red-breasted Nuthatch, Black Vultures (sitting in the trees by the parking area), Carolina Wrens, and many others.
Reservoir Road is the longest road to the water, and includes a long stretch of relatively rough (gravel) driving. The best views of the water and sky are found here, and there are numerous hedgerow and thicket birds in the area, including Purple Finches. I've seen Bald Eagles, Red-tailed and Red-shouldered Hawks, Tundra Swans, and many of the larger local bird species from this landing. A gated road runs north from here along the power lines all the way to the dam. Reservoir Road is also used by county dump trucks and garbage trucks, so be careful.