The Sheltering Junk

By Rachel Preiser|Saturday, February 01, 1997
RELATED TAGS: ECOSYSTEMS, POLLUTION
Shooter’s island, sitting at the north end of a narrow strait between Staten Island and New Jersey, has long been a maritime dumping ground. Some 30 acres of abandoned barges, tugboats, and other ruined vessels ring the ten-acre island. Because the odd barge or detached mast occasionally drifts into busy shipping lanes, the Army Corps of Engineers made plans a decade ago to remove the debris. Recently, however, the Army abandoned those plans, largely because of Kathy Parsons, an ecologist at Manomet Observatory in Plymouth, Massachusetts. Parsons has found that the floating junk is vital to the health of wading birds throughout New York Harbor.

Parsons knew, as did many local bird-watchers, that a wide variety of wading birds--including black-crowned night herons, snowy egrets, and cattle egrets--nested on Shooter’s Island. She wondered how the destruction of the island’s shoals of debris would affect the birds. While the Army Corps was debating what they should do, we began putting together a long-term database of the wildlife resources there, says Parsons. We wanted to know whether there were habitat values in the drift that weren’t being provided in natural marsh sites. Parsons found that the floating debris surrounding the island is essential to the health of the bird community. Last spring she persuaded the Army not to destroy the drift; instead the Army will build a sheet-metal fence around most of Shooter’s junk to keep the habitat intact.

Parsons kept a weekly count of the numbers and types of birds visiting randomly selected sites on several islands in New York Harbor during the nesting seasons between 1985 and 1993. The overall abundance of birds on Shooter’s Island was similar to that of nearby drift-free islands like Prall’s and the Isle of Meadows. But the waterbirds on Shooter’s Island were different in one key respect: three-quarters of them were immature. That’s very significant, says Parsons. It suggests that the drift is acting as a nursery for these birds--like a learning lab.

Donning a pair of cut-off rain pants, Parsons waded into the drift to see what might make it such a rich habitat for fledgling waterbirds. From 1991 to 1993, she and her team took monthly samples of salt-marsh grasses growing in the drift and compared them with marsh grasses from Prall’s Island and the Isle of Meadows. Not only was the drift grass about 30 percent taller, but there was twice as much of it. Parsons thinks that by intercepting the tide, the accumulated debris may allow nutrients to settle in its tranquil tide pools, thus providing a fertile muck for grasses.

Minnows also like to feed in that muck, so Parsons wasn’t surprised to find that tide pools in the drift harbored twice as many minnows as the natural marsh sites. Since minnows are prime bird food, the abundance of fish also suggested why young birds might prefer the drift. There may be greater numbers of young surviving on Shooter’s Island because they have that added advantage of a nearby, abundant prey area, says Parsons. It’s perfect for young herons that are just learning to fish.

The island’s role as a natural nursery was put to a severe test a few years ago. When an underwater pipeline burst and spilled 567,000 gallons of oil into the harbor in 1990, fish numbers crashed and the populations of wading birds on surrounding islands fell. But the birds are slowly coming back, and Parsons believes the junk at Shooter’s has been instrumental in their recovery. We saw a major abandonment of the other two islands in that area, and a sort of retrenching at Shooter’s, she says.

By 1998, the Army will have sunk a sheet-metal fence into the artificial marsh around Shooter’s to enclose 75 percent of the island’s most valuable asset, preserving it for the birds and perhaps keeping it out of shipping traffic. We’ve come up with a plan, says Parsons, that’s going to ensure the existence of herons in that area for quite a while.
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