The 1,012-acre South unit includes three acquired properties that historically were used for dairy production. One of the largest great blue heron rookeries on the lower Columbia River is on this unit. In 2000, this rookery contained more than 350 active nests; by 2001, however, the nesting site was abandoned, most likely due to drought conditions affecting forage or an increase in bald eagle activity in the area. A second newer rookery, also on the South unit, grew substantially to 142 active nests in the same year.
In 2004, the first phase of restoring Shillapoo lakebed wetland vegetation