Osprey Survey Shows Species is Thriving

There were 301 active osprey nests counted between July 1 and late August in the towns of Southampton, Southold, Riverhead, East Hampton and Shelter Island.

The East End osprey population has been flourishing, with the number of active nesting sites increasing more than 50 percent in the region since 2014, according to this year’s osprey survey conducted by the Group for the East End in conjunction with other organizations.

There were 301 active nests counted between July 1 and late August in the towns of Southampton, Southold, Riverhead, East Hampton and Shelter Island, not including privately-owned Gardiner’s Island, which was not surveyed, according to the Group’s vice president Aaron Virgin, who oversees the survey work.

That compares with 198 active nests counted in 2014, when the Group began conducting the annual survey with help from The Nature Conservancy, the Eastern Long Island Audubon Society, North Fork Audubon and staff from various town agencies.

Mr. Virgin attributes the bird’s population increase to plentiful stocks of menhaden. He said an osprey can bring up to 20 menhaden, also known as bunker, to its chicks every day. Mr. Virgin attributes the rise in menhaden stocks to tighter limits on industrialized fishing in the region.

Five-year averages for the number of nesting sites in each of the five East End towns are 196 in Southold; 106 in Southampton; 64 on Shelter Island; 28 in East Hampton, and 12 in Riverhead.

The densest population of breeding ospreys is on the North Fork, Mr. Virgin reported, including Fishers, Plum and Robins Islands, which alone account for 60 nesting sites. About half of the East End’s active nesting sites are in Southold Town, which Mr. Virgin attributed to the “myriad creeks, coves and small bays adjacent to Peconic Bay and Gardiners Bay.”

Shelter Island had the highest occupancy rate, with 80 percent of known nesting sites in use this year, Mr. Virgin reported. Its five-year average is 69 percent. Riverhead had the fewest nests with 19, only about half of which were occupied. “This is due to the town’s large shoreline frontage on the Long Island Sound,” Mr. Virgin wrote, “where there are only roughly one dozen osprey sites due to strong winds and surf during storm events, and minimal habitat along the Peconic Bay.”

He found that East Hampton Town’s nests were the highest locally in terms of successful breeding, with a five-year average of 1.58 chicks for each nest. Scientists consider any average of one or more the sign of a stable population as each chick matures and reproduces within the lifespans of its parents.

“Without question,” Mr. Virgin wrote, “East Hampton appears to be showing the fastest growth, particularly in the Accabonac Harbor area, where more than a dozen nests could be observed from a single spot” this summer.

Southampton, the largest of the East End’s towns in terms of geography and human population, “has had a very steady population during the past 20 years,” Mr. Virgin wrote, which he called a testament to the Group’s earlier days in osprey conservation.

Formerly known as the Group for the South Fork, when it was based in Bridgehampton, the Group in past decades set up osprey nesting poles around the town. “Perennial areas along Dune Road, Shinnecock Bay, Mecox Bay, along with newer sites on Scallop Pond, Long Beach and North Haven have kept the osprey population not only stable but modestly increasing, particularly in the backcountry areas of Water Mill and Bridgehampton,” Mr. Virgin wrote. The Group now has offices in Southold.

Interestingly, Mr. Virgin predicts that the osprey population on the East End will stabilize as the bald eagle’s numbers continue to rise here. During this year’s survey, bald eagles were encountered at multiple sites, including Scallop Pond in North Sea, Hubbard Creek in Flanders and Kellis Pond in Bridgehampton, he said; bald eagles were already in residence on Shelter Island. “I have heard of other bald eagle sightings on the North Fork, Plum Island and points west,” Mr. Virgin said.

Because they compete with ospreys for food — and are known to attack nests and kill chicks — it is expected that bald eagles will put a lid on the osprey population. “It’s going to be very interesting very quickly once a critical mass of bald eagles is breeding on the East End,” Mr. Virgin wrote, “It may not happen next year or within the next five years, but it’s coming.”

The population of both birds plummeted from the 1950s into the 1970s because of the pesticide DDT, which was used in many regions to fight mosquitos. The chemical thinned their egg shells, which were crushed under the weight of adult birds. Both eagle and osprey populations began a slow rebound after DDT was banned in 1972.