NEW YORK -- Each year, 1,700 tankers bring 18 billion gallons of oil into New York Harbor. And each day huge barges carry 14,000 tons of garbage to the Fresh Kills landfill on Staten Island.
The harbor, also heavily trafficked by container ships, gravel boats, tugs and pleasure craft, hardly seems a good place for fish-eating birds to settle and raise their families. Surely they would never choose to live among the flotsam and jetsam and just plain trash washing up on the shores, or among wrecked ships and docks and long-abandoned buildings on islands that look nothing like a wildlife refuge. Surely elegant snowy egrets or black-crowned night herons would never call a place like that home.
Yes, they would and they do.
In the last two decades, undeterred by PCBs, noise, odors and other types of pollutants, exploding populations of herons and egrets, glossy ibises and double-crested cormorants have joined the ubiquitous gulls that call the harbor home. Thousands of long-legged waders have no compunctions about nesting in unkempt spots or dining on fish and shellfish from polluted water. Although, to humans, several of the harbor islands and their environs may look like slums, to the birds they resemble an Everglades paradise, replete with food and nesting sites and free of threats from people, raccoons and most other predators.
Returning from the edge
Several of the species now thriving here had been threatened with extinction; others had never been known to nest near New York City. Their expanding presence in the harbor is testament to the incredible resilience of nature, once it is given half a chance.
The birds live, breed and feed on islands never visited and rarely noticed by most New Yorkers despite their proximity to the five boroughs: North and South Brother Islands between Queens and the Bronx; U Thant Island in the East River, a hefty stone's throw from the United Nations; Shooter's Island in the Kill (or stream) Van Kull; Prall's Island and the Isle of Meadows in the Arthur Kill between Staten Island and New Jersey; and Swinburne and Hoffman Islands in lower New York Bay between Brooklyn and Staten Island.
These harbor islands, along with the islands of Jamaica Bay and a few islands east of the Bronx in Long Island Sound, comprise fewer than 1,000 acres, said Dr. Paul Kerlinger, an environmental consultant. Yet Kerlinger reported in the current issue of Living Bird Quarterly, the annual surveys he conducts with volunteers from the New York City Audubon Society, that the harbor islands alone are breeding grounds for nearly 1,000 pairs of black-crowned night herons and several hundred pairs each of snowy egrets, great egrets, cattle egrets and glossy ibises.
This is not to mention the rapidly expanding populations of double-crested cormorants, sleek black fish eaters that had not been known to nest in New York Harbor until eight years ago. There are now about 960 breeding pairs of cormorants in the harbor, where the federally protected birds have so far escaped persecution by fishermen who elsewhere view them as competition.
"This certainly says something about the quality of the water," said Peter Mott, president of the New York City Audubon Society, as he toured the islands by boat recently. Mott said that in 1960 no egrets or ibises were nesting in the harbor and a mere sighting of an ibis in 1950 "was so unusual that I played hooky from school just to see one."
He credits the Clean Water Act of 1972 for the fact that the harbor is now hospitable to myriad aquatic species -- from snails and tiny shrimp to crabs and bait fish -- and the long-legged wading birds that depend on such fare.
"In 1970, if you put mummichog into the Arthur Kill in summer, it quickly died for lack of oxygen," he recalled. Mummichog, a salt marsh fish used for bait, is a favored food of black-crowned night herons, among other waders. The Clean Water Act mandated a reduction in the amount of fecal and other organic matter that could be contained in the effluent of sewage treatment plants. This meant that there was less oxidizable material in the processed sewage, which in turn meant that oxygen levels in harbor waters into which the treated sewage was dumped could rise to a point that could sustain aquatic life.
"When the level of dissolved oxygen falls below 3 parts per million, the water can't support most fish life or invertebrate life," Mott said. "Now in the Arthur Kill, 64 percent of the freshwater comes out of sewage plants."
But organic matter from sewage is not the only contributor to an oxygen shortage in waters surrounding a big metropolis like New York. Mott said that runoff from the rain and snow that reaches the harbor has very low oxygen levels.
One need not go any farther than tiny U Thant Island, named for the former secretary-general of the United Nations, to witness the consequence of cleaner harbor waters. Cormorants have built nine nests in the island's two spindly trees, and the other day the residents of those nests were feeding furiously on a school of small fish that had become confused by a rip in the current north of the island.
Cormorants are not the only inhabitants of this rocky outcropping in the East River. Their companions include a young herring gull and a young black-backed gull, "both of which probably hatched on the island," Mott said, and several spotted sandpipers. In addition to the trees, there is a gridwork of steel tubing erected as a memorial to the former secretary-general.
A little farther north on South Brother Island, in the shadow of Riker's Island, about 850 cormorants have claimed squatter's rights. In fact, there are so many of the birds that their noxious droppings have killed most of the trees where they nest and threaten to render the island inhospitable to black-crowned night herons, which are still the most abundant long-legged waders in the harbor. Here and on neighboring North Brother Island, where a long-defunct sanitarium once housed Typhoid Mary, "about 1,000 black-crowned night herons and 200 snowy egrets raise their chicks every year," wrote Margaret Mittelbach and Michael Crewdson in their book "Wild New York" (Crown, 1997).
On Shooter's Island, once a thriving shipyard at the foot of Newark Bay and now a veritable sanctuary for wading birds, hundreds of great egrets and snowy egrets build platter-sized nests on the island's low-growing cherry trees each spring, Mittelbach and Crewdson noted. Nesting egrets were first spotted on this shipping channel island in 1974, and in each successive year there are more.
Productive salt marsh
Dr. Katherine Parsons of the Manomet Bird Observatory in Massachusetts and collaborators, who studied bird colonies in the harbor for a decade, found the most productive salt marsh among the shipwrecks at the west end of Shooter's Island. There, surrounded by the decaying wrecks and dry docks, "hundreds of young herons get their first food-finding experience," Mott said.
The cormorant population on Shooter's Island was set back about five years ago when someone set fire to some of the old wooden structures that supported their nests. Mott said dry docks are ideal nesting places for cormorants because their excrement cannot destroy them.
An oil spill in 1990, which dumped 567,000 gallons of fuel oil into the Arthur Kill and contaminated the surrounding salt marsh, took its toll on glossy ibises, which depend on marsh snails for sustenance, and snowy egrets, which feed along the edge of the marsh on mummichogs and silversides.
But with the cleanup and salt marsh restoration undertaken by the city's Department of Parks and Recreation, the birds have returned. The restoration was financed with $1 million from a trust fund established by Exxon Corp. to settle charges that it was responsible for the spill.
"Altogether, on island rookeries throughout New York Harbor, more than 4,000 wading birds are nesting," Mittelbach and Crewdson wrote in their book about New York City's wildlife. "These birds have chosen their sites so well that most New Yorkers will never see a heron's nest. In addition to being almost totally inaccessible (the harbor acts like an enormous moat), the islands are near sparsely populated, industrial areas where, despite passing boats, the birds can keep a relatively low profile."
Pub Date: 01/10/99