My wife, Pat, caught the sight through her camera lens. As she lowers the Nikon, her face lights up with a broad smile, half joy, half wonder.

"I just love this," she says.

We are in Blackwater National Wildlife Refuge in the Great Marsh of Maryland's Eastern Shore. Blackwater Lake, a 12-square-mile tidal pool, stretches in front of us. Thousands of Canada geese waddle on the mud flats. A bald eagle stands sentry on the lone trunk of a long-dead loblolly pine. A squadron of ducks leaps out of the water and flies overhead on whistling wings. A heron stares through the surface of the water, looking for lunch.

The 27,000-acre refuge makes you feel as if you have traveled to a remote, raw frontier of nature. But we are just 15 minutes from U.S. Route 50, a six-lane highway lined with hotels, fast-food franchises and big-box stores that cuts through the city of Cambridge, 140 miles southwest of Philadelphia.

The marsh draws more than 165,000 visitors a year, mostly in the early spring and the fall. About 60 percent of Americans live within a day's drive, according to the U.S. Fish and Wildlife Service (FWS).

They come to see the winter home of 35,000 Canada geese, 15,000 snow geese and tundra swans, and thousands of ducks and loons - even white pelicans. Tens of thousands of migrating birds make the refuge a stop on the Eastern Flyway, so the FWS maintains a series of ponds and cultivates more than 450 acres to provide food.

It also is the year-round home of more than 130 bald eagles, the largest East Coast population of the national birds north of Florida, the FWS says.

The beauty of Blackwater, however, hides the fragility of the marsh.

"Sea level is rising even faster than we thought," says Dixie Birch, the supervisory wildlife biologist at Blackwater. "We continue to lose the marsh at an alarming rate. More and more is going underwater. It could be gone in 2025 or even 2020."

In the recently remodeled Visitors Center, staffed by volunteers from the Friends of Blackwater, a monitor displays the live feed from a camera over an eagles' nest, where the female has just laid two eggs to start her new family.

"They lay their eggs in the winter," a volunteer explains. "They incubate them for 32 to 36 days before they hatch."

Males and females take turns sitting on the eggs to make sure they stay warm and unmolested.

It's easy to explore this wildlife refuge. You can drive from the Visitors' Center to Wildlife Drive, which winds for five miles along waterways, woods and marsh. Several short trails branch off the drive to get you even closer to the wildlife.

Around a corner in the drive, the horizon opens up, and you realize why Blackwater has become known as the "Everglades of the North." Open expanses of water are framed by islands covered with pines and tall grass. Most of the migrating geese and swans winter there, congregating in flocks of hundreds to thousands.

The air is full of the sounds of birds. The honking of an unseen flock off to the west carries across the water like a distant war chant.

As we drive though a forested section, Blackwater's version of a traffic jam brings us to a halt. Four cars are stopped on the shoulder. A half-dozen people are standing in the roadway, aiming binoculars and cameras with telephoto lenses toward the pines.

We join them. One of the men lowers his camera, points to the trees, and says in a reverent church whisper, "Back there, about 20 feet up, two bald eagles."

The pair of national birds is looking back at us with bored gazes, slowing turning their heads to get a better view. A cyclist stops to join us, followed by a young couple with a baby in a stroller. We all watch quietly. No one talks. No motorists blow their horns in impatience.

A chevron of geese passes overhead. We are in their home.

The refuge also has hiking trails and three marked water "trails" for paddlers who want to explore deeper into the marsh. The FWS recommends that paddlers take guided tours to help navigate the maze of rivers and streams.

While the Chesapeake Bay is rising from the effects of global warming, the land is also sinking under the water at a rate of about 100 acres a year. The lake is really the drowned Blackwater River; its serpentine bed, once lined with tall grass, has slipped under the surface over the last 75 years.

For more than 185 years, Blackwater has been the victim of upstream mistakes. A canal dug by slaves in 1820 turned the freshwater river and marsh brackish, killing trees and wildlife. Nearby canneries that shipped seafood and vegetables around the world for the first half of the 20th century used so much water that the land is slipping away. Rainwater runoff from housing developments sends pollutants into the marsh.

If the cycle is not reversed, the marsh will continue to disappear, Birch says.

Marshes are crucial to the environment, she adds.

"They are a major spawning area for shellfish and finfish and an important habitat for bald eagles and migratory birds and the endangered Delmarva fox squirrel," she explains. "If the wetlands are lost, they will have nowhere to go.

"Someone has said that wetlands are like the kidneys in a person - they filter out wastes and help clean up the bay."

Federal and state agencies are working on long-range plans to restore the marsh.

A major success has been the eradication of nutria, Birch says. The beaverlike rodent, native to South America, was brought to the area in the 1940s to supplement the native muskrat fur trade. With no natural predators, the nutria population expanded rapidly. Their favorite meal happens to be the roots of marsh grasses. They were eating the marsh to death.

The other great hope for the restoration is to use soil dredged from the bottom of the Chesapeake Bay shipping channel as fill to replace the subsided land. The dredged soil is being used to rebuild Poplar Island in the bay.

Blackwater's preservation has drawn national attention. When a developer wanted to build a resort, golf course and thousands of homes at the headwaters of the Little Blackwater River, the Chesapeake Bay Foundation got 35,000 people to sign a petition opposing the project. Last year, state lawmakers negotiated a reduction in the size of the project and bought 750 of the 1,080-acre tract for parkland.

The marshes in Dorchester County have always been sparsely populated. Most of the villages have more gravestones than occupants. Those who farm, hunt and fish the area for a living have to contend with oppressive summer heat and some of the meanest mosquitoes on the Delmarva Peninsula.

Until the Civil War, slaves worked much of the land. Harriet Tubman, the famed Underground Railway conductor, was born on the Brodess Plantation a few miles from Blackwater. A museum dedicated to her life is in Cambridge.

The road from Cambridge to Blackwater runs through incredibly flat farmland and tall stands of pine. South and west of the refuge, a network of narrow, two-lane roads takes you into the heart of the marsh. At high tide, the road often disappears under water. For miles, there are no man-made structures in sight. Frequently, the horizon disappears as the water meets the sky.

There are great vantage points to see the colors of the day and the changing wildlife of the seasons. As we headed out of the preserve, several photographers were setting up their cameras on tripods - facing west - to capture the day's last rays reflecting on the lake.

Exploring the Eastern Shore

Cambridge. Twelve miles from Blackwater National Wildlife Refuge, this colonial Chesapeake Bay seaport still has a working commercial harbor. But the industrial waterfront is now overshadowed by new condo towers, and the workboats are being replaced by pleasure craft.

The hardworking Dorchester County seat of 11,000 has had its economic difficulties, but it is going through a revitalization. Several blocks of 19th-century storefronts have been converted into galleries and antique stores. A January fire damaged four buildings, but plans are under way to rebuild.

A housing boom on the city's outskirts is mirroring the condo construction on the harbor. The city marina, next to the Cambridge Yacht Club on the Choptank River, has been built into a major yachting facility, with a new breakwater and boat slips.

Dorchester County calls itself the "Heart of Chesapeake County," and it is a hub for exploring Maryland's Eastern Shore. Lodging includes B&Bs in town, chain hotels on Route 50, and the luxurious Hyatt Regency Chesapeake Bay Golf Resort, Spa & Marina on the riverfront. The Hyatt, with its expansive indoor-outdoor pool complex, waterfront rooms, restaurants, tennis courts and golf course, is worth the trip.

Hooper Island. Ten miles down the road from the Blackwater National Wildlife Refuge is this watermen's community, which is actually three islands connected to the mainland by bridges. Islanders have made their living pulling crabs, oysters and fish from the bay for more than 300 years. The archipelago is known for its historic graveyards, bald eagles and fishing charters.

Taylor's Island. North of Hoopers Island, this is another watermen's hamlet with its own collection of fascinating churchyards.

St. Michaels. Home of the Chesapeake Bay Maritime Museum in neighboring Talbot County. The resort village is noted for its shops and waterfront dining.

Easton. A Rockwellian county seat with tree-lined streets and a historic downtown. The Avalon Theater, a performing-arts venue that attracts nationally known entertainers, is 20 minutes away.

Oxford. You can drive to this quaint village northwest of Cambridge and take the Oxford-Bellevue Ferry, one of the oldest ferries in the country (it runs from March through November) across the Tred Avon River. Drive to St. Michaels, then loop back through Easton to Cambridge.

Most of the roadways have wide shoulders and are popular bike routes.

Getting there

From Philadelphia, take I-95 South to Delaware Route 1 South. Take Route 896 to U.S. Route 301. In Maryland, turn left on Route 213 South and then left on Route 50 East to Cambridge. Note: Friday-evening traffic on Route 50 is often clogged with Baltimoreans heading to the beaches of Ocean City, Md.

Blackwater National Wildlife Refuge
2145 Key Wallace Dr.
Cambridge, Md.

410-228-2677

The Visitors Center is open 8 a.m. to 4 p.m. Mondays through Fridays and 9 a.m. to 5 p.m. on weekends. There is a $3 fee for vehicles on Wildlife Drive and $1 fee for pedestrians or cyclists.

For information

Blackwater NWR site www.fws.gov/blackwater

Friends of Blackwater www.friendsofblackwater.org

Eagle Cam (bald eagle brooding on their eggs) www.friendsofblackwater.org/camhtm2.html

Lodging, restaurants, attractions and events in Dorchester County

www.tourdorchester.org

Lodging, restaurants, attractions and events in Talbot County

www.tourtalbot.org

- Dick Cooper

Eagle Festival

The eighth annual Eagle Festival is scheduled

8 a.m. to 4 p.m. Saturday at Blackwater National Wildlife Refuge. The free event will include bird walks, a how-to session on wildlife photography, and talks about global warming and the history of the refuge. Programs for children will run from 9 a.m. to 3:30 p.m. There will be live music, and civic groups will run food concessions.

For more information: www.fws.gov/blackwater/eaglefestival.html.