A bald eagle crossed over Bartholomew's Cobble before sunrise on Saturday, September 19, ahead of anyone with a clipboard. By the time the Berkshire Environmental Action Team's 17th Annual Berkshire Biodiversity Day officially opened at noon, the day's first entry in a 24-hour species count was already written down. What followed was a full weekend of people turning over logs in the rain, netting insects, scraping algae off rocks, and photographing a wildflower most drivers on Weatogue Road have passed a thousand times without noticing.
This is the part about the Cobble that tends to get skipped in the usual write-ups: it's not a place people finished discovering decades ago and now just visit. Every year BEAT sends scientists and amateur naturalists out for one continuous day-and-night stretch to count everything alive in a given patch of Berkshire County, and every year, when that patch is Bartholomew's Cobble, the count turns up things that surprise people whose job is not supposed to include surprise.
Why the Ground Itself Keeps Producing Firsts
The reason has less to do with luck than with rock. The Cobble sits where two different kinds of stone meet the Housatonic River: quartzite, which is acidic, and marble, which is alkaline. That collision creates a stretch of soil chemistry that swings from one extreme to the other over a short distance, and plants that would never tolerate each other's neighborhood elsewhere end up growing within feet of one another here. It's the same mechanism behind the property's fern count, one of the richest in North America at 53 species, and it's part of why the site holds more than 800 documented plant species overall, according to reporting from The Berkshire Edge.
The reservation was named a National Natural Landmark in October 1971, a designation that turns 55 this fall. Fifty-five years of federal recognition hasn't slowed the pace of new finds. More than 250 bird species have been logged here over time, including the bald eagle that opened this year's count, along with bank swallows, bobolinks, and pileated woodpeckers, according to background compiled on the property's Wikipedia entry. That's not a fixed inventory. It's a running tally that keeps getting longer.
What Twenty-Four Hours of Looking Actually Looks Like
The people doing the looking this year had names, and the Berkshire Eagle's on-the-ground account gave them faces. Chelsey Simmons led a tree identification walk, stopping to show the difference between opposite and alternate leaf patterns. Ryan Goss drove down from Williamstown to photograph a bladder campion in the field. Kay Hurley came from Carlisle fresh off a gathering of 44 lichenologists in Maine, and spent Saturday examining lichen up close.
Tom Tyning, a professor who has led the amphibian and small mammal walk for years, got the kind of weather herpetologists actually want on Sunday morning: rain. He sent his group into the woods to turn over logs, and found what he was looking for in the red-backed salamander, an amphibian with no lungs that can't survive in a pond. "They lay their eggs inside rotting logs, and the moms stay with them," he told the group, describing how the eggs cluster like grapes while the mother guards them against predators as small as shrews.
Not everyone at the Cobble that weekend was hunting salamanders on purpose. Ben Nickley found a baby snapping turtle in the road and stopped to show it around. Momo Chang-Pierce spent time at the oxbow of the Housatonic watching birds. John Wheeler worked through a field guide on Sunday, foraging and identifying fungus. And at two and a half years old, Calvin Borgert-Herleikson was among the youngest people there, tagging along with his father, Brett, more interested in looking at the frogs Tyning's group turned up than in touching them.
Kay Hurley's reason for making the drive from Carlisle carried its own weight. She came in part to honor Joe Warfel, an amateur arachnologist and spider photographer whose work had been published in journals, who attended the BioBlitz every year until he died last year. Friends of his have kept teaching their kids to leave the spiders alone with a phrase that's become its own small tradition:
"Don't step on Joe."
Meanwhile, algologist Karolina Fucikova spent the weekend under a microscope, working through more than 50 species of algae collected from the Cobble's water, plus a handful of amoebas. Hurley called having a microscope partner on-site "kind of fun," a small detail that says something about how specialized this event actually gets. This isn't a nature walk with a checklist. It's working scientists doing real inventory work in a place most people drive past on the way to Great Barrington.
A Site That Was Already the Bar to Clear
BEAT rotates the Biodiversity Day to a different Berkshire site each year. The 15th annual event, held on the Berkshire Community College campus in 2024, tallied 503 species by the end. The 16th, held elsewhere, drew more than 130 attendees and logged 389. Landing this year's count at Bartholomew's Cobble put the event at the one property in the county already known for the deepest biodiversity around, which means the comparison isn't really fair. This is the site other sites get measured against.
The final tally for this year's count wasn't posted as of this writing. What's already on record from Saturday and Sunday, the pre-dawn eagle, the dozens of algae species, the active amphibian turnout in the rain, suggests the Cobble held up its end of that reputation without needing a final number to prove it.
Walking It Yourself Before the Next Thing on the Calendar
The Cobble doesn't require a BioBlitz badge to visit. It's open daily from sunrise to sunset, with admission at five dollars for nonmembers and a dollar for children between six and twelve, free for Trustees members. Pets aren't allowed, a rule the property enforces to protect the plant and wildlife diversity that makes it worth visiting in the first place. Parking is on Weatogue Road, and the visitor center keeps seasonal hours, so a call ahead to 413-229-8600 is worth it before a trip.
The Ledges Trail is the easiest introduction, a half-mile loop around the twin rock outcrops that give the Cobble its name. From there, the Tractor Path climbs toward Hurlburt's Hill, rising to 1,000 feet at a 20-acre upland field that straddles the Massachusetts-Connecticut line, with views up the Housatonic River Valley that are close to their best right now, as foliage moves through the county. History-minded visitors can follow the Hal Borland Trail to the Colonel John Ashley House, the oldest standing house in Berkshire County and the site tied to Elizabeth Freeman, known as Mumbet, whose 1781 lawsuit for her freedom helped end slavery in Massachusetts.
The Cobble makes sense as a morning plan this October, especially with something else on the calendar three weeks out. On Saturday, October 17, the Southern Berkshire Chamber and the Town of Sheffield are holding the first annual Sheffield Fall Festival on the Town Green, running from 3 to 9 p.m. with the Green closed to traffic and turned into what organizers are calling a Pumpkin Plaza. A hike through the Cobble in the morning and a first-year town festival in the evening is a reasonable way to spend a Saturday in a town that, this fall, has more than the usual amount going on.
If Sheffield's version of a good weekend, quiet trails in the morning and a new town tradition finding its feet by evening, is the kind of daily life you're picturing for yourself, Diane Thorson knows this ground well enough to talk you through what it actually feels like season to season. Schedule a consultation with her when you're ready to talk about it.
