To protect a large group of coastal birds nesting on Norton Point Beach, The Trustees of Reservations have closed the stretch of barrier beach between Chappaquiddick and Katama to off-road vehicles. The closure came Friday when a number of birds hatched, and will remain in place until further notice.

Fishermen, sunbathers and swimmers, however, will find that much of the two-and-a half-mile beach remains open to passive recreation. Access by foot is available from the Left Fork in Katama and from the beach on the Chappaquiddick side.

"There is a lot of outside beach for people. We are doing the best that we can do to open areas on the outside," said Kate Conde, a ranger and bird expert with the Trustees.

The coastal birds under watch include piping plovers and least terns, the latter of which have established a large colony near the center of the Norton Point property. A number of least terns just hatched; Ms. Conde said there are 14 three-day-old tern chicks and five one-day-old chicks. And there are an additional 14 eggs that could hatch any day.

"I have a plover nest on one side of the road and terns on the other side of the road. Cars have been able to move along the road, but once the terns hatched there were a lot of little birds running around," affirmed David Belcher, the Trustees superintendent for Chappaquiddick.

The nonprofit conservation organization took over management of the beach this spring under a five-year agreement with Dukes County. Much of the Trustees' emphasis is on the protection of the threatened piping plover, a bird that travels the Eastern seaboard and is having a difficult time because of a shortage of undisturbed nesting habitat. The bird is protected by state and federal regulations. The Trustees also monitor the bird on Cape Pogue Wildlife Refuge.

This spring, four exclosures were built to protect nesting birds of both species and their hatchlings. An exclosure is like a cage that works in reverse. Rather than pen animals in, an exclosure keeps predators away from the nests. At Norton Point, these predators include skunks, raccoons and some birds. Ms. Conde said a fifth exclosure was installed yesterday to protect another piping plover pair. Those birds are not expected to hatch until Fourth of July weekend.

"We had Norton Point closed for two days in the beginning of the season because [piping plovers] hatched. It was a tough place for them. The high tide had washed away two of the four eggs in the nest. The birds ended up rolling the other two away from the water. The remaining two eggs hatched on Monday, June 12, but unfortunately the chicks disappeared within a day and a half," Mr. Belcher said. A likely culprit was a red-tailed hawk that had been seen in the area, according to Ms. Conde. The beach was reopened on Wednesday, June 14.

"I am excited about the least tern colony," Mr. Belcher said. "There hasn't been one to survive this long in at least 10 years."

Credit for the success of the colony goes both to the Trustees staff and to Island fishermen, who have kept an eye out for the endangered birds.

"My staff has worked hard to put up exclosures around the whole colony. It is a two-foot-high wire mesh with high fencing, to keep the skunks out. That is why we have chicks now," Mr. Belcher said, adding:

"The fishermen have been very cooperative. They understand what we are trying to do. We are not trying to close the beach. What has been nice is that they have been seeing what we have been doing. They get a bird's-eye view of what we are doing to protect the birds," Mr. Belcher said.