Every year, thousands of snow geese and tundra swans descend on the farm fields surrounding a small Pennsylvania lake for one of the biggest meals of their lives.

For more than two weeks, the birds graze on corn stubble, other leftovers and winter wheat in the farm fields around Middle Creek, a 400-acre lake near the Lebanon and Lancaster county line in Southeastern Pennsylvania. They drink the lake's fresh water and swim along its shores, putting on a show for the thousands of birders who know just when to come for the best viewing.

Then, around the first week of March — give or take a few days — the birds take flight. The tundra swans will soar 10,000 feet into the air, their wings spanning nearly 6 feet. They fly until they reach the North Slope of Canada and Alaska, where they will breed. Some years, more than 3,000 tundra swans fill the skies of Middle Creek, their 18-pound bodies majestic against the snowy foothills of the area's rural hamlets. The snow geese will join them in the air, more than 50,000 strong, honking and flapping their black-rimmed wings all the way up the St. Lawrence Seaway to the top of Quebec.

It is an unforgettable sight. And it is one that a group of naturalists, government officials and conservationists fear won't last much longer.

Middle Creek's 1,700 acres are protected land, owned by the Pennsylvania Game Commission since the early 1930s and operated as a preserve since the 1970s. But the thousands of acres of farmland around the lake and preserve are privately owned. Under an agreement with the Game Commission, farmers leave 25 percent of their crops on the ground for wildlife to consume.

For decades, no one worried too much about development in this pocket about 10 miles north of Ephrata. It would be too far to be a bedroom community for Hershey or Harrisburg, and besides, the township didn't have sewer.

But that changed this year, when Heidelberg Township received nearly $9 million in state funds to install a sewer line that is connected with Lebanon. Now, the hamlets of Kleinfeltersville and Schaefferstown, and all of the wild birds' feeding grounds between them, have the potential for development.

There was no question that the towns needed the sewer line, as some of the septic systems were failing. The sewer service had been in the plans since 1969, said Jen Snyder, office manager for Heidelberg Township. And the zoning in this part of Lebanon County, which is on the edge of the Chesapeake Bay watershed and close to the Delaware River watershed, remains rural.

But that is not of much comfort to George Gress, a land steward with the Nature Conservancy who manages a preserve near Middle Creek.

"One of the things that I've personally seen in these small towns is that once you get the sewage capacity, the building increases," he said. "It's kind of a magnet for development that seems to explode."

Gress and a group of concerned conservationists have formed the Middle Creek Initiative. Its goal is to persuade farmers to keep farming and preserve the land through easements so that the swans and geese will not lose their feeding grounds.

It's not a new initiative for Lebanon County, which has preserved 16,000 acres of farmland over the last 25 years. But it's a much bigger push than the county has made in the past, said Chuck Wertz, district manager of the Lebanon County Soil Conservation District. Lebanon County has 100,000 acres of farmland that are eligible for easements. It has not been as successful as its neighbor, Lancaster, which has preserved 25,480 acres in about the same amount of time.

"What you need to make this work is millions of dollars," Wertz said, "and we don't have any funding of real substance."

What the initiative does have, though, is commitment. Jim Binder, the manager of the Middle Creek Preserve, organized the players, which include Pennsylvania Audubon Society, The Nature Conservancy, Ducks Unlimited, the U.S. Fish and Wildlife Service, the Pennsylvania Highlands Coalition and the Lebanon Valley Conservancy.

The initiative's first step was to watch where the birds ate and how much they consumed. The staff at Middle Creek put transmitters with cameras on several of the birds, so they could see where they traveled. They found that the birds needed a wide open area for their staging and feeding. Even if they only used the middle of a 50-acre field, Gress said, they actually needed the whole area — because they would not visit a site if development was at its edge.

The second step was developing a scoring mechanism for farms. Once the scientists and naturalists figured out where they went, they could determine which farms were most valuable.

The conservationists plan to start door-to-door visits soon. They hope that they will be able to raise money from various conservation groups to help finance easements.

It will not be cheap or easy, Wertz predicts, especially with the land more valuable now with sewer capacity. Preserving a 100-acre farm could cost about $250,000. Selling that land to an interested developer, though, could net the farmer millions of dollars.

Middle Creek was not originally on the migration route for swans and geese. They tended to fuel up to the southwest, on the Susquehanna Flats, feasting on Bay grasses. But after Tropical Storm Agnes in 1972, much of the grass beds were lost, and the swans and geese found another fuel stop here on their way north after spending the winter in North Carolina and on the Eastern Shore of Maryland and Virginia.

By the 1990s, close to 8,000 swans arrived annually and more than 125,000 snow geese visited, according to a history of the property provided by the Game Commission. This year, a count found a high of 55.000 snow geese on Feb. 28, 3,300 tundra swans on Feb. 12, and 4,200 Canada geese on Jan. 7.

Other birds and waterfowl come, too. There is a heron rookery and a sizable population of black ducks. Schoolchildren from the surrounding areas come here on field trips in elementary and middle school.

The people involved in the Middle Creek Initiative do not want to think about what will happen if their push to preserve the farms doesn't work. The first time the birds lost their food source, they found Middle Creek. If they lose Middle Creek, they may find other farms and quarry lands in the Lehigh Valley and Lancaster. But for how long? Will those places eventually become subdivisions, too?

"This is a unique, value-added way to protect this land," Wertz said. "This is where people feed, but it's also where swans feed. If the farmlands go by the wayside, will they find something else, or not? I really don't know."

For information on the Middle Creek Initiative, visit www.portal.state.pa.us/portal/server.pt?open=514&objID=924478&mode=2.