THOMASTON – For more than a century, Weskeag salt marsh in South Thomaston was an elevated mud flat with tall grass kept dry by man-made ditches that drained the water at high tide. It was always an area where shorebirds such as great blue herons and egrets could be found. But in the past two years, thanks to human intervention, it has become a place where an assortment of uncommon birds and rare European species congregate during their migration south.

Three years ago, biologists with the U.S. Fish and Wildlife Service along with the Maine Department of Inland Fisheries and Wildlife, which owns the marsh, received a federal permit to restore it to its natural state. By plugging up the ditches, the biologists have allowed saltwater ponds to form again.

Now, it is a veritable way station for migrating breeds and a convenient access point where birders can view spectacular shorebirds such as hudsonian godwits, white-rumped sandpipers, and marsh hawks, all from the Arctic.

“People always birded it,” said USFW biologist Ron Joseph, who applied for the permit. “Now that the water is back on the high area, there are shore birds migrating through from Greenland and Labrador from July through October.”

Weskeag was first drained back in the 1800s, according to Joseph. Large ditches 5 to 8 feet across were cut into the high swamp from the bay to allow settlers who lived along the coast to harvest salt hay for their cattle. Joseph said ditches were also dug early in the 1900s as a way to control mosquitoes. The result was a radically changed habitat.

In drained salt marshes, tidal waters flow back into bays, leaving only shallow water that can evaporate, preventing the survival of aquatic plants and insects.

At Weskeag, most of the 12 ditches have recently been plugged using material from excavated areas. This keeps the water from receding at high tide, allows the water table to rise, and creates wading pools for shorebirds.

Using sod taken right from the marsh and with the help of an expensive tractor called a Positrack, USF&W and DIF&W have created plugs to dam the ditches. The specialized tractor is needed because its wide base distributes its weight, allowing it to move over the soft ground without sinking in.

“We’re putting water back into the high marsh. When the tide comes up, the shorebirds can’t feed down on the flats. Now they come up into the marsh to feed in the pools,” Joseph said.

DIF&W started to purchase parts of the marsh in the 1960s and owned the entire area by the mid-1970s, according to wildlife management supervisor Gene Dumont.

About 20 years ago, Dumont said, his department attempted to restore the marsh using older technology, but the wooden plugs were washed away by the receding tides.

Again in the early 1990s, Dumont said, the Department of Transportation attempted to fill in the ditches, as part of mitigation work it was doing, but water was able to seep around the wood plugs.

Dumont said the latest technology for restoring saltwater marshes only evolved in the past 10-12 years as efforts up and down the East Coast were increased to preserve habitat for migrating birds.

Since the project began in Weskeag in 1997, it has proceeded slowly, based on the availability of the excavation equipment, but it is now nearly completed. The result is already apparent.

New aquatic plants have brought insects and small invertebrates which, in turn, have attracted small fish. The growth throughout the food chain has set the table for migrating shorebirds. Already, Joseph said, the bird sightings at the area have increased significantly.

“Now birds like the hudsonian godwits stop here…. They make a long-distance flight, flying for days on end, from the Arctic to South America,” he said. “They’re stopping in Weskeag to feed on insects. They’ll end up in Argentina in another month.”

As Joseph, a lifelong birder, explained the science and mystical nature of migratory shorebirds, he sounded both excited and dumbfounded at the success of the birds’ “epic journey.”

“Sandpipers will fly from the Arctic Circle down to South America. They are genetically programmed to make the journey,” he said. “They follow the sun and the stars. This is true with almost all shore birds.”

Joseph is delighted to have helped provide a marsh in the midcoast area for the birds – and birders. The largest salt marsh in the state is farther south in Scarborough.

While not rare, some birds seen at the Weskeag marsh recently were magnificent for Maine, most of them migrants. As the tide came in from Thomaston flats in the afternoon, the thin and dainty legs of the lesser yellowlegs slowly moved into the marsh in large numbers.

Also seen were dunlins, a small bird with an odd down-turned bill. Only 27 were seen last year in Maine, although they are not considered uncommon here.

There were also hundreds of semipalmated sandpipers, birds that fly in flocks that twist and turn, revealing flashes of their brown nape and white bellies.

The most familiar birds were seen in abundance, including a half-dozen great egrets, a number of great blue herons, and several snowy egrets, birds with droopy white plumage so in demand by hunters in the early 20th century.

The swamp is easily found off Buttermilk Lane, a road that serves as an example of how man’s interference in the landscape has reduced its biodiversity.

Joseph said because the culvert the road passes over is small, the tidal circulation on the side away from the ocean is affected. The result, he said, is the incursion of the invasive plant framites.

When the salinity changes in a marsh, Joseph said, the invasive plants take over. This can be seen on the non-ocean side of Buttermilk Lane, where cattails have moved into the marsh. While cattails are native to Maine, Joseph said, they do not exist in the middle of a marsh under normal conditions.

However, on the ocean side of the road, where the marsh has been reclaimed, the restored health of the ecosystem is evident by the multitude of plants, animals, and insects, even by the abundance of mosquitoes.

“The [insects] are important to the food chain. They have helped restore it,” Joseph said.

Deirdre Fleming covers outdoor sports and recreation for the NEWS. She can be reached at 990-8250 or at dfleming@bangordailynews.net.