For over 70 years, ecologists at Great Gull Island in Long Island Sound have managed an important feat for the survival of two migratory coastal birds. With support from thousands of volunteers and researchers they have helped restore roseate terns and common terns to the island after their populations collapsed in the early to mid-20th century when Great Gull Island was used by the US Army as part of the coastal defense system.
Despite their success, however, the scientists remain concerned about the birds’ survival on this 17-acre island east of Plum Island and Orient Point at the tip of the North Fork of Long Island.. Even with steady progress, including over 40,000 adults and chicks populating the island by 2025, they worry that any number of large-scale threats can result in a sudden collapse of the populations, according to Joan Walsh, a researcher at the American Museum of Natural History, which owns the island.
In 2022, Walsh and her colleagues, Margaret Rubega of the University of Connecticut and Peter Paton of the University of Rhode Island applied for a grant with the Long Island Sound Futures Fund to support the island’s first comprehensive conservation plan. They wanted to address looming threats such as sea level rise, erosion, animal predation, disease, failing infrastructure of the island’s legacy infrastructure, human disturbance and existing and new invasive plants, a threat that had been partially addressed in prior years, but needed more attention. The Futures Fund awarded the University of Connecticut $400,000 to develop the plan, using a science-based and action-oriented process called “Open Standards for the Practice of Conservation.” The plan, completed in August, was developed with support from 30 technical experts and dozens of community stakeholders. Through the process 17 direct threats were identified, and with focused decision making, 10 strategic responses were selected and prioritized.
“Great Gull Island is a very complicated place, so you have to allow yourself to come in with your ears wide open to hear what the other experts have to say about priorities,” said Walsh. “I thought it was a really amazing process to a be a part of.”
For decades, said Walsh, ecologists with volunteer support succeeded largely by responding to immediate threats to the bird populations, such as removing debris left over from the military installations. The conservation plan fills a critically important need to be proactive to prevent large-scale ecological impacts from threatening the bird populations.
“When Margaret, Peter and I came on to codirect the project, we realized that we needed a comprehensive plan to help us rank the threats to understand what is most important,” said Walsh. “It’s very easy to get distracted by a single chick falling into a hole. Right? That’s a tragedy and it may take you quite a while to fix that small problem so that no more chicks fall in that hole when your time is better spent finding how you restore the whole area so that no chicks fall into any holes over the next 50 years.”
High on their action list was to safeguard against an accidental introduction of ground animals such as rats, mice, mink, and raccoons to the island. These mammals can prey on the terns and their chicks or spread disease. In 2025, the co-directors applied and were awarded additional funds from the Futures Fund to develop a strategic response for biosecurity, which will include protocols to ensure that staff don’t accidentally introduce rodents in the boats they use to commute to the island.
“Rats are our number one concern,” said Walsh. “They are voracious predators and reproduce rapidly. And rats along the coast are very common, and warming winters are allowing rats to persist in higher numbers. We have to have a real security plan for every one of our boats to ensure that we don’t get rats out there. We don’t have any ground predators.”
Another high priority is to enhance the existing plan for controlling invasive plants. It will build upon one that had also been supported with a Futures Fund grant in 2012. That plan resulted in a successful effort to remove invasive wild radish, a plant that had blanketed much of the island and could entangle and kill young terns and replacing it with native seaside goldenrod. Walsh said that in the past after a heavy rain the leaves of the plant would fall down “like a mat” on young chicks. “It was killing hundreds of chicks every year,” she said. “The adults couldn’t get to them if it rained and they would get hypothermic and die.”
Roseate and common terns share similar features such as a forked tail and a black cap. Roseate terns, designated an endangered species by the federal government, are thinner and, when breeding, have a reddish color on their breast and belly, which is how they get their name. They inhabit Great Gull Island from May to September for breeding before they head south for the winter. In 2025, there were about 2,331 pairs of adult roseate terns on Great Gull Island, which represents about 36 percent of the population of breeding pairs for that species in North America. Also in 2025, the island had about 11,190 pairs of common terns, which represents about 10 to 15 percent of the population in the northeast, but about 90-95 percent in Long Island Sound. This species is designated as threatened in New York and Connecticut.
The terns have populated Great Gull Island for centuries, but they largely disappeared starting in 1897 when the US Army began using the island as part of a coastal defense system. After World War II, the Army decommissioned the island and sold it to the American Museum of Natural History for $1 for the sole purpose of restoring it as a bird sanctuary. Today, legacy infrastructure, such as tunnels that could potentially collapse and lead to salt-water intrusion, are imminent threats that concern ecologists. But scientists and resource managers have also recognized that there are ecological benefits from the 19th and 20th century development. For example, a stone revetment was built to fortify the island when it was a military base today protects the island from erosion and sea level rise. The Army also elevated part of the island for some of its’ military installations, and as a result today some of the terns nest in areas that are as high as 40 feet above sea level. While other tern habitats in Long Island are losing ground to sea level rise and erosion, and changes in land use, Great Gull Island is expected to remain a bird habitat for decades to come as well as a source population for any efforts to restore colonies lost in other Long Island Sound habitats or elsewhere in the northeast.
“Pete Dunne, the nature writer, talks about the metaphor of the game of musical chairs for habitat loss,” said Walsh. “We just keep taking away their chairs and there just aren’t many places left for them to go.
“And that’s happened in our lifetime. When I first started working at Great Gull Island (in the 1980s), my job was to go to the surrounding islands during the day. We had a Boston Whaler and we’d look and see how many of our birds were nesting in all these small colonies all around Great Gull Island. Most of those colonies don’t exist anymore because of sea level rise or because of land use changes. So, in this game of musical chairs, you know, Great Gull is more than a chair – we’re kind of a couch.”
Visit the Great Gull Island website to download the plan, learn more about protecting the terns, and see more photos as well as videos about life on the island.
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