At the Bird-Houston Site we spent all week excavating features. On the newer part of the site, where people lived from around 1830 to 1920, several of the features are shallow pits filled with brick rubble. We think these are the remains of brick piers, a simple kind of foundation you can still see at many old farms throughout Delaware. When a building was abandoned or replaced, the intact bricks were often salvaged to be used in another project, and the broken pieces were tossed back into the hole. So shallow pits full of broken bricks are a common kind of archaeological feature. After we dug all the brick rubble out of one of these features, we got a surprise. The soil underneath was not clean subsoil. It looked disturbed, with many small patches of dark gray soil. After digging around for a while we figured out that the gray patches were tunnels. Our first thought was that these were groundhog tunnels, since groundhogs are the great tunnelers of rural Delaware. But the tunnels seemed small for groundhogs. Then we found these bones. They haven’t been examined by an expert yet, but they certainly look like a lower jaw and broken skull of Rattus norvegicus, the brown rat. So the tunnels were rat tunnels, and the disturbed soil was evidence of a rat nest. This confirms our theory that the brick feature was an old foundation, since brown rats almost always live underneath buildings. Using clues from the wild species around a site to understand human culture is called environmental archaeology. So we have just done a little bit of environmental archaeology ourselves, using the presence of a rat nest to confirm the location of a building at the Bird-Houston Site.