The group of open-grown oaks directly north of the Natatorium and east of the Lakeshore Path bridge over Willow Creek tells of a time when fire and/or grazing kept the land an open oak savanna. The oaks themselves represent several species—bur oak, white oak, and black oak (with possible introgressive hybridization involving whites and burs). The area also includes an important Indian burial mound group.
Overtime this stand of scattered trees became choked with the growth of numerous weedy, woody species. Between 2008 and 2010 Physical Plant Grounds Department staff under the direction of Preserve management removed invasive buckthorn shrubs and fast growing trees like boxelder opening the mature oaks and effigy mounds to full view. Following the removals Preserve staff, interns, and volunteers seeded and carefully inserted native plant plugs of savanna species to restore the barren groundlayer.
The emerging savanna habitat attracted a nesting pair of great-horned owls in 2010 who have for several years successfully fledged owlets and attracted a lot of admirers. The open habitat and high perches in mature trees seem to benefit the owl’s ability to hunt for the small mammal prey (voles, mice, rabbits, squirrels) that forms a large portion of their diet. In addition, the Preserve’s resident pair of sandhill cranes can often be found foraging under the tree canopy.
Restoration of the site continued in Spring 2013 with the removal of two Trachte sheds used for many years by the Rec Sports Department. The building sites and the driveway that led to them were seeded with savanna species.