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Harbor Herons Nesting Survey Reports
2011 Nesting Survey Report
Summary By Kate Walker
Research Associate Elizabeth Craig has sifted, tabulated, and recorded for posterity the results of the 2011 NYC Audubon Harbor Herons nesting survey. The survey's report, which Craig submitted in December, paints a comprehensive picture of the shore-loving birds who called the harbor, rivers, and islands of New York City their home this season. The Harbor Herons survey has gathered data for nearly 30 years. In her report Craig noted many interesting trends emerging, as well as a few smaller, but equally poignant, occurrences.
Eight species of long-legged wading birds (waders) and double-crested cormorants were recorded in this year's survey. The waders include: black-crowned night-heron; yellow-crowned night-heron; great egret; snowy egret; little blue heron; tricolored heron; glossy ibis; and great blue heron. The survey also investigated any gull nesting activity. The survey extended from Huckleberry Island, which lies in the western portion of Long Island Sound, through the East River to islands at the very mouth of New York Harbor, and east to Jamaica Bay.
One significant trend noted is that Hoffman Island, near the mouth of the Hudson, continues to show an increase in the overall numbers of target species birds nesting there. Hoffman has become a real center for activity and diversity. Now that Hoffman has been established as a strong nesting colony for black-crowned night herons, snowy egrets, great egrets, and the glossy ibis, Craig hopes that more waders will continue to gravitate towards this colony.
For herons overall, the results of the survey were mixed. Yellow-crowned night heron nest numbers remained stable, and the great egret saw a harbor-wide increase, as did the little blue heron. However, black-crowned night herons and snowy egrets both saw nesting decreases. Tri-colored heron numbers remain low, here at the northern edge of their range. The most alarming tally was a 35% harbor-wide nesting decline for the glossy ibis, largely because of its decline on traditional nesting stronghold Canarsie Pol.
Canarsie Pol has historically provided reliable habitat for nesting waders. Jamaica Bay, where several islands including Canarsie Pol were surveyed, showed a mixed trend this year, however. The survey showed that nesting species have been moving around a lot within the bay. Reasons for the movement aren't clear, according to Craig. The survey recorded a dramatic 59% decrease in wader nests and a 76% decrease in double-crested cormorant nests on Canarsie Pol alone. It is quite possible the dense vegetation of Canarsie Pol prevented the surveyors from getting a thorough count, Craig says. Her concern about these decreasing numbers is tempered, somewhat. The nesting colonies, with the exception of the glossy ibis, may simply be shifting to other locations in Jamaica Bay, or even the greater harbor, as birds seek out the best resources available.
A small event did bring Craig great excitement: The survey recorded the nest of a great blue heron on Goose Island this year. "Great blues" are generally mainland-nesters, which may explain why the great blue has previously not dwelled in the Greatest City on Earth. As for the cattle egret and green heron, which were not recorded this year, they are also mainland-nesters. Craig was neither surprised nor concerned that these species had not returned to NYC to nest this year.
Huckleberry Island is one location that causes Craig real concern. The survey hasn't recorded any active nests there in the past few years, quite possibly because of predators such as raccoons.
Cormorants continue to display a very stable population in New York Harbor on the whole. These birds don't just stick to land masses as places to build their nests; several aids to navigation in the harbor bear their nests, so those were also included in the territory of the survey. Double-crested cormorants do fine in close company with each other, as well; U Thant Island, which is a mere quarter of an acre, housed 38 double-crested cormorant nests this year. Fourteen pairs of great black-backed gulls and two pairs of herring gulls were also able to squeeze onto the island. Unfortunately Cormorant colonies can push out other colonies or degrade habitat, so they can be challenging bedfellows, particularly for waders.
While double-crested cormorants have a very stable population, gulls are experiencing something very different. Craig estimates that the gull population may have decreased by as much as 50%, harbor-wide, given the very thorough survey that was performed in 2010. Fortunately, Susan Elbin, NYC Audubon's Director of Conservation and Science, has received funding from the Eppley Foundation for a new study that may provide some insight. This study will look at herring gulls at various points around the harbor, to figure out what impact organic contaminants and heavy metals might be having on them. The study will also look at how those same contaminants affect a variety of nesting species—including some waders, the Canada goose, and gulls—on one of the East River islands.
Craig hopes that further study will help identify the sources of nesting population decline on such sites as Canarsie Pol and Huckleberry Island. We can hope that Elbin will be able to find the root of some of the gull population decline through her new study, as well. In short, many important discoveries await NYC Audubon researchers, as they continue to track the health and well being of our harbor herons and friends. To learn more about what we've learned from many years of monitoring these birds, please join NYC Audubon for Susan Elbin's lecture on Wednesday, January 16: Up to Our Knees in the Mud--What We've Learned from Foraging Waders. You may also read this year's report as well as past reports by clicking on the links provided below.
2011 Harbor Herons Nesting Survey
Click here to view full report.
2010 Harbor Herons Nesting Survey
Click here to view summary results.
Click here to view full report.
2009 Harbor Herons Nesting Survey
Click here to view full report.
2007 Harbor Herons Nesting Survey
Click here to view update.
2006 Harbor Herons Nesting Survey
Click here to view update.
2005 Harbor Herons Nesting Survey
Click here to view update.
2004 Harbor Herons Nesting Survey
Click here to view update.
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