Following the first overnight freeze of the season, I opted for a hike at Rockbridge Memorial State Park (south of Columbia) yesterday afternoon. There I took the Grassland Trail that winds across tallgrass prairie and passes a number of sinkholes in the limestone bedrock. Woodlands cluster at the sinkholes, offering prime roost and hunting sites for hawks and owls that inhabit the park.
On my visit, the late October sun offered little warmth to moderate the chilly, northwest breeze. Fortunately, the cool conditions invigorated the birdlife as I strolled through the preserve; eastern bluebirds, American crows and American goldfinches dominated the grassland while a host of woodpeckers, blue jays, nuthatches, chickadees and titmice noisily rummaged through the sinkhole woodlands. In thickets along the woodland borders, I observed several groups of white-throated sparrows, the first winter residents that I have seen this season. American kestrels perched on the powerlines while a pair of red-tailed hawks circled above the prairie, stoking the ire of the resident crows.
The sinkholes, some of which hold water, are the product of collapsed caves; indeed, an extensive network of caves and underground streams lies beneath the Park, coursing through a thick slab of Mississippian limestone. At the surface, the sinkholes drain water from the surrounding prairie, giving rise to ponds, marshes, thickets and woodlands; dry sinkholes also offer protected retreats for a variety of hunters, including snakes, long-tailed weasels, raccoons, fox and coyotes.
