A Wood Thrush Serenade

Before he spent decades caring for patients, Mark Thomas learned to listen to the woods.

“I was always outside growing up,” says the retired family physician, remembering his childhood 30 minutes north of Philadelphia, where he developed a fascination about birds, plants, and the natural world. “My parents encouraged natural history.”

Thomas traces that connection even further back, to his Quaker ancestors who arrived in the region in 1683. Generations later, his own path would lead him to a small stretch of Burlington County that would become the focus of his life’s conservation work.

In 1988, while beginning his residency in Family Medicine at Memorial Hospital of Burlington County in Mount Holly — now Virtua — Thomas looked for a place to live. He chose Pemberton Borough, where the north branch of the Rancocas Creek winds through.

“The assets [of the area] appealed to me,” Thomas recalls, finding a place to “watch birds and for relaxation” during those long residency training days at the hospital.

Then he read John McPhee’s “Pine Barrens” and became captivated by the beauty of Rancocas Creek.

He describes his fascination in an online blog in 2024 on the Rancocas Conservancy website. 

“It’s intimate, human scale, and [has] leafy-green corridors,” Thomas writes. “The sound of spring peepers lured me into the valley that April. The vibrant leaves of skunk cabbage had begun to unfurl in the warming mud along the creek.

“This particular day I wandered past the canoe rental in the borough and past the two dams, over which flowed tannin-brown waters. 

“Following the creek-side path that matched the curve of the stream, I came to a subtle hillside rising to the south, where a grove of American beech, with their smooth gray skin and straight stature, filled the slope,” Thomas continues. “Their nascent green leaves were opening in elongated curls of light-filled translucency. Into this lush scene, directly in front of me, a wood thrush swooped in and perched above me, some 15 feet away. 

“It sang for 10 minutes in the flute-like melody that has captivated me since childhood. The completeness and wondrous quality of the experience triggered an immediate, and permanent, inspiration to protect this place.”

And so, the mission of Rancocas Conservancy was born. It’s a land trust that buys and preserves properties along the Rancocas and its tributaries to prevent their development, according to its website. 

Today, they are recognized as the leading land trust in the watershed, responsible for the permanent preservation of approximately 2,500 acres of land and 12 preserves. The Conservancy is accredited by an independent program of the Land Trust Alliance. An accreditation seal affirms national quality standards — sound finances, ethical conduct, responsible governance and lasting stewardship — are met.

From the beginning to the present

Thomas gathered the names of people who might have an interest in exploring the opportunities to preserve land along the Rancocas Creek and its branches. The search took him to municipalities, county and state agencies, where he searched for those who might protect the natural beauty and resources of the Rancocas Creek watershed.

“The first person to respond was Barbara Rich,” Thomas recalled.

He had never met or heard of Rich before then. Thomas quickly found a strong environmental conservation ally in Rich.

“She immediately agreed [to help] … no questions asked,” he said. “Back in the day, it was basically stuffing and stamping envelopes.”

Rich is one of the four founding members of Save the Environment of Moorestown, a grassroots organization with a mission to preserve, protect, and enhance the natural environment of Moorestown for today and for future generations, according to its website. It was founded in 1972.

She co-founded the Rancocas Conservancy with Thomas and is still involved as a Board of Trustees member.

“We held our first meeting at Smithville Park on June 19, 1989,” Thomas said. “We received our non-profit status as the Rancocas Watershed Conservation Foundation on September 12, 1991.”

The Rancocas Conservancy began its successful “Rancocas Journal” in Fall 1994. In 1995, they were awarded grants from the Green Acres Department of the New Jersey Department of Environmental Protection (DEP) to acquire natural lands in the Rancocas Creek watershed. 

“It was a beautiful thing,” Thomas said of Conservancy development, noting they were completely volunteer run. “It was a proud moment.”

In 1998, the Conservancy unveiled its first preserve, the Michael Stavola-Pemberton Beech Woods, the same location where the wood thrush sang to Thomas years before. 

“On these 46 acres, where 34 houses were to have been built, a beech woods, whose landscape provided a unique grove of beechwoods succession in a relatively undisturbed setting, was preserved in perpetuity,” Thomas wrote in the blog. “Subsequently the preserve has been enlarged to 61 acres, comprising most of the remaining open space in Pemberton Borough.”

Over the intervening years, largely through volunteer effort, the Conservancy has protected approximately 2,500 acres of land in the Rancocas Creek watershed, including upland headwaters, large intact acreage of swamp and wetlands, and corridors along the branches of the Rancocas Creek.

Today, a newly reinvigorated board works diligently to curate the Rancocas Conservancy’s 12 preserves throughout Burlington County. Education and advocacy go hand-in-hand with land acquisition.

Volunteers are present at environmental fairs, presentations are made at allied non-profit meetings and municipal activities, and they assist in local preservation efforts.

Thomas is now retired and had most recently served as vice president of the Board of Trustees. His retirement was announced in a blog post in December 2025. Along with being a generous donor himself, he continues to serve as a volunteer and trustee emeritus.