Last weekend I visited Audubon’s Rocky Hill Wildlife Sanctuary in southeast Groton, straddling the Ayer line, in the Snake and Rocky hills. A few years ago I had heard that a colony of herons existed somewhere in that area, but I had never made it over there to investigate. The great blue herons flying over Route 2 and standing on their nests in the swamp’s dead trees reminded me to seek out the Rocky Hill heronry.
In addition, Shaker historian Ned Quist’s recent talk at the Harvard Historical Society about Harvard’s great Shaker barns also inspired me to visit the sanctuary. I was already curious about the Shakers’ trips to “the Ledges” to get stone for the mill dam, which are mentioned in the Harvard Shaker Village journals of 1858. So when Quist showed a map of the 1,000 acres once held by the Shakers, I wondered if that land north of Route 2A known as Snake Hill was where the ledges were.
Indeed, the map of Audubon’s Rocky Hill Wildlife Sanctuary highlights ledges as well as a Heron Trail. The sanctuary, located in a suburban development of large houses on the Groton-Ayer line, is a 10-minute drive from Harvard’s Shaker Village. When I arrived, I parked the car along the curb rather than risk scraping the Prius’ undercarriage on the asphalt curb of the parking lot entrance.
After stopping to study the information panel at the edge of the parking lot, I walked over a rise in the land, passing a sculptural outcropping of rock before reaching the edge of a wide power line cut. There, I was struck by the lack of traffic sounds. I stopped to listen to the birds singing in the low, dense shrubbery under gigantic pylons. A blue bird fluttered in front of me before diving into the foliage.
The trail cut through the shrubbery to the edge of the forest where two unobtrusive sign posts about 20 feet apart indicated trailheads in opposite directions: the left one for the Rocky Hill Trail or the one to the right for the Heron Trail. A wide woods road is between the two.
The Rocky Hill Trail footbed is, in many places, composed of exposed granite where the earth has worn away, almost like walking on hard, smooth pavement. All around are walls of rock covered in green mosses, rock tripe, lichen, and polypody fern. Distinctive boulders sometimes jut out from the ledges overhead. The wall of rock rose up out of the ground to high above my head.
After passing through an area of high ledges, I entered a woodland terrain with scattered boulders and came to a low, rocky ridge that overlooked a large body of water, indicated on the map as Lower Long Pond. Overlooking the pond, the rocky outcrop created a string of little cave-like rooms indicated on the map as Shelter Ledge.
The woodland path became less rocky and began to climb through a forested landscape high above the water, where beaver lodges can be seen from above. The light shone on the backs of turtles sitting on logs in the water.
The field artist Barry Van Dusen, in his book “Finding Sanctuary,” notes that in April 2015, looking through his telescope, this high viewpoint provided a direct view into the heron nests.
Herons often nest in dead trees surrounded by water, where their eggs are safe from predators. The Heron Trail wound around the water’s edge to an area of dead trees standing in water, but those trees were thin, tilting or lying in the water. Through binoculars I saw one old, unoccupied nest.
The trail intersects with the Ovenbird Trail heading toward Snake Hill that soon intersects at some impressive boulders with the Chestnut Oak Loop Trail. This trail skirts a swamp with cattails on one end of its loop and long high ledges of Snake Hill on the other side of the loop. True to its name, chestnut oak leaves lay scattered on the trail near tree trunks with deeply ridged bark, and two garter snakes slithered by.
On the trail back, I thought about how the herons who once nested in the dead trees until the trees could no longer support their nests had probably moved on and how industrious beavers and people moved in. I saw birds and the footprints of animals beneath the humming power lines. Perhaps the green-covered ledges of rock had never been disturbed in a search for building materials after all, but the old woods roads are still there and not yet overgrown. A swallowtail butterfly fluttered around the stone outcrop that reminded me of an ancient sculpture or temple.
The trail system is easy to follow: blue markers take you away from the parking lot, and the yellow ones take you back. Intersections are marked with the trail names. (If you deviate from the Audubon map and marked trails, be competent in using GPS.) The wide, well-maintained trails are easy to moderate, with a few steep but short rises that may require careful footing. A 4- to 5-mile walk could be pieced together, but much shorter walks are possible also. Be sure to review the sanctuary’s regulations concerning animals and the use of trails. There are no entrance fees.
Margaret Kusner is a retired art teacher, a lifelong artist, and walker.
