Yesterday, I took my Ornithology class to Woods Reservoir to look for ducks and other waterbirds. Many of these species overwinter here in the south before heading back north to breed in the boreal forest, the prairie-potholes, or the arctic. The weather was as warm and balmy as I’ve experienced in January and the duck count reflected this: we see fewer ducks during extended warm spells, presumably because they have not been pushed south by hard weather up north. However, we did see a good assortment, with the coots leading the count, as usual.
Many of the waterbirds that we saw are fish-eaters (loons, grebes, herons, mergansers). Unfortunately for them, Woods Reservoir is contaminated with PCBs and the fish bioacummulate these toxins and pass them up the food chain to the birds. The PCBs came from the Air Force’s Arnold Engineering Development Center (Woods Reservoir was built in 1952 to provide cooling water for the site). The Tennessee Department of Public Health has issued an advisory that recommends no human consumption of catfish caught from Woods Reservoir. They recommend that consumption of other fish species be limited to one fish per month. The birds (and the many fishermen at the lake) have evidently not heard this advice.
PCBs are found in the lake sediment and fish accumulate these pollutants in their bodies, especially in fat. Manufacture (but not use) of PCBs was banned in 1979, but the chemicals are very persistent, so linger in many ecosystems. PCBs were used at AEDC from approximately 1952 to 1990 and they are believed to have entered Woods Reservoir via streams draining contaminated soil at the site (2007 TDEC report).
Two non-duck highlights were a Bald Eagle and a Northern Harrier. The eagle gave us a great display, soaring in great ascending circles over the lake against the blue sky. Its slow, self-assured flight and eight-foot wing span embodied unfashionably grand qualities: majesty, imperialism, and hauteur. Bald Eagles may be ill-tempered, bad-breathed fish-scavengers, but they’re awesome nonetheless. The harrier flew across the lake with lazy wing beats as the sun set.