Simon Lindop-Taylor and his son Orlando walk Wing's Island, behind the Cape Cod Museum of Natural History, in Brewster.
(MICHELE McDONALD/GLOBE STAFF)
BREWSTER -- As a small group emerges from the woods behind the Cape Cod Museum of Natural History, nature walk leader Dot Platt gestures out to the water visible from the hillside. "That's Cape Cod Bay," she says, "but thousands of years ago it was a lake. When the glaciers melted and the sea level rose, the ocean rushed in."
That bit of geological lore is merely prologue for the 1.3-mile round-trip walk from the museum across a marsh, through a young forest, and to the outer dunes, beach, and tidal flats of Wing's Island. The journey from museum to beach and back traverses most of the important ecosystems of Cape Cod, save the surf zone and white cedar swamps of the Outer Cape. In effect, the trail expands the museum's indoor exhibits by putting those plants and animals in grand context.
As Platt subtly points out, the boundaries of land and water are always changing on Cape Cod, and sometimes it's hard to tell one from the other. Indeed, unless the tide is very high, it's difficult to discern that Wing's Island is an island. Salt marsh nestles at the ankles of its uplands, looking for all the world like solid ground.
"But when we have the big spring and fall tides," she says, "you can't get across without a boat. People were stranded out there this spring, and they just had to wait out the tide."
We are literally walking on water as we tramp single file down the planks laid atop the spongy marsh. To our right, adult ospreys arch their backs and spread their wings on their nest, making a fearsome show to keep us at a distance from their three chicks. To the left, perched on a craggy limb that extends over the marsh, a very large bird preens its dark breast. We try binoculars and a telephoto lens, but with the afternoon sun behind it, the backlit bird remains mysterious. White bars under the wings suggest a juvenile bald eagle.
Green metal boxes stand every 50 yards or so along the marsh, and Platt leads us to one next to the walkway. "It's a greenhead fly trap," she says, inviting us to look inside where a few dozen of the sharp-biting flies buzz angrily against the top screen. "If you've ever been bitten by one of these, you'll understand why we can afford to lose a few honeybees in the traps. Besides, the bees are smart and usually find their way out."
Tiny streams dissect the marsh, and every one teems with tiny fish. "This is one big nursery," Platt says. The marsh almost seems to vibrate with life. Small fiddler crabs pop in and out of holes in the stream mud banks, so ghostly that only their movement gives them away. Red-winged blackbirds sway on tall reeds and swallows glide erratically across the grassy marsh, decimating the insect population. Platt bends down and plucks what looks like a tiny gherkin. "Sea pickle," she explains. "It's sour and salty."
When we reach the island, Platt says there's no evidence that John Wing, who purchased the land in the 1650s, ever lived here, but he definitely harvested salt hay from the marsh and may have farmed the uplands. Since the late 19th century, the open land has grown up in pitch pines, red cedar, and a mix of black, white, and scrub oaks. Winding around them are Virginia creeper, honeysuckle, and poison ivy. If ever a plant loved Cape Cod, it's poison ivy. Platt points out the creeping vine, the woody shrub, and single-stemmed upright plants along the trail. "Three leaves," she warns. "It's all poison ivy." Everyone on the walk then backs up half a step.
Recent archeological digs have turned up pottery, stone tools, and shell middens of Native Americans, who apparently used Wing's Island as a staging ground for harvesting the Brewster flats. A replica of a Native American stone solar calendar -- presumably used to gauge the seasons for planting corn -- occupies a small clearing.
As the trail nears the outer dunes, the taller trees give way to low-lying beach plums and a profusion of rosa rugosa, or beach roses. The tide is just past high, so the riches of the Brewster Flats lie tantalizingly beneath shallow water. The Cape Cod Museum of Natural History does schedule special summer low-tide walks for children. During "Mudflat Mania," the kids examine the worms, mollusks, crustaceans, and other life-forms of the tidal zone.
For adults, it is enough perhaps to ponder the vagaries of sea and shore, a landscape that changes by the minute, a world of clams and fish, ospreys and eagles, and yes, even poison ivy.
Cape Cod Museum of Natural History
869 Route 6A, Brewster 508-896-3867; ccmnh.org
Adults $8, seniors $7, children ages 3-12 $3.50. Guided walks to Wing's Island offered twice on weekdays, once daily on most weekends; free with museum admission. "Mudflat Mania" fee: member adults $4, seniors $3, ages 3-12 $2; nonmember adults $6, seniors $5, children $4. Discount if purchased with museum admission. Remaining dates include Aug. 17, 20, 21, and 22.
Patricia Harris and David Lyon, Cambridge-based freelance writers, can be reached at harris.lyon@verizon.net. 
© Copyright 2008 Globe Newspaper Company.
