City Claims Final Private Island in East River

South Brother Island, seven acres of dense forest, bittersweet vines, flocks of wild birds and little else, is a speck in the East River — and a glimpse of what the rest of the city might have looked like thousands of years ago.

Historically overlooked and unwanted, it changed hands for $10 in 1975, despite being located in the middle of New York City.

But South Brother, the last East River island of any significant size to remain in private hands, will finally get its due today when it is formally transferred to the city as part of a complex $2 million deal brokered by the Trust for Public Land and financed with federal money secured by United States Representative José E. Serrano.

“The idea of buying an island — I mean, how many people get to buy an island?” said Mr. Serrano, whose district includes South Brother.

South Brother, situated between the Bronx and Queens and within sight of the Rikers Island guard towers, will most likely be left as it is, officials said, preserved as a nature sanctuary and administered by the city’s Department of Parks and Recreation.

The island — the smaller sibling of the better known North Brother Island, which is 500 feet to the north and once the quarantine home of Typhoid Mary — suddenly became a desirable property precisely because it had been unwanted for so long.

Neighboring islands, including North Brother, became sites for hospitals that treated infectious diseases like typhus and tuberculosis and for mental hospitals, power plants, jails, homeless shelters and cemeteries for the indigent. But South Brother, neglected by humans, turned into a prime nesting spot for birds and a migration stopping point for such New York City exotica as the great blue heron.

“It is a natural jewel,” said Clark Wallace, project manager for the Trust for Public Land, a nonprofit conservation group.

In addition to several types of herons, the island’s bird population includes ibises, oyster catchers, cormorants and egrets. In its forest are locust, white mulberry and black cherry trees, covered by thick tangles of oriental bittersweet vines that cover trees and ground alike. Because there are no predators on the island, many birds build their nests on the ground.

K. Jacob Ruppert, whose great-great-uncle Jacob Ruppert Jr. owned the island and was a co-owner of the New York Yankees in the early 1900s, said South Brother was a bird paradise when he paid his only visit in 2004.

“There’s no beautiful lagoon,” he said. “It’s a mound of bird poop. But there are beautiful birds. I never thought I could walk up to a swan on her nest. The ground is nothing but bird droppings and broken egg shells.”

But humans, even if few have ever set foot on the island, have had an impact.

During New York City Audubon’s annual surveys of the island, volunteers have found dead birds entangled in fishing lines and other debris. Adult birds have been found dead on or near nests that contained unhatched eggs, and Mr. Ruppert said he spotted a television set that had washed ashore.

Maria Torres, president and chief operating officer of the Point, a nonprofit group that is working to revitalize the Hunts Point section of the Bronx, and Mr. Serrano said they had been interested in buying South Brother for the public since 1997. But the owner, Hampton Scows, a Long Island sand and gravel company, had not been interested in selling until recently.

Official with Hampton Scows declined to comment, as did the company’s lawyer, Michael McMahon.

But once Hampton Scows signaled its willingness to sell, the Point and the Bronx-based Wildlife Conservation Society, which had received federal money through Mr. Serrano’s efforts to buy private land along the Bronx and East Rivers for public use, agreed to pool their money to come up with the $2 million asking price.

Unlike better-known East River islands like Randalls, Roosevelt and Rikers, South Brother’s past is murky.

Both North and South Brother Islands were claimed by the Dutch West India Company in 1614, according to “The Other Islands of New York,” a book by Sharon Seitz and Stuart Miller, and both were originally named “De Gesellen.” (The term was translated as “the companions.”)

The islands soon passed into the hands of the English, but remained undeveloped for almost two centuries because of the treacherous currents surrounding them, according to the book.

South Brother may have been a base for Union soldiers during the Civil War, and in about 1894, it was purchased by Jacob Ruppert Jr., a brewing magnate who bought the Yankees with Col. Tillinghast L’Hommedieu Huston in 1915. (Mr. Ruppert’s tenure in baseball included the purchase of Babe Ruth from the Boston Red Sox, the opening of Yankee Stadium and eight World Series titles.) Mr. Ruppert built a yacht house on South Brother, and amateur baseball games were held on an adjacent field. Legend has it that Ruth would occasionally show up to practice his swing, swatting balls far into the East River.

After Mr. Ruppert’s summer home burned down in 1909, South Brother went through another long fallow period. The island changed hands several more times until 1975, when Hampton Scows bought it for $10.