Great Gull Island: From Military Fort to Global Seabird Sanctuary

Located in the town of Southold in Suffolk County, New York, Great Gull Island is a 17-acre sanctuary that separates the Long Island and Block Island sounds. While it sits less than a hundred miles from the bustle of New York City, this remote outpost has evolved from a fortified military base into one of the most critical avian habitats in the Western Hemisphere.

The World’s Largest Tern Colony

Today, Great Gull Island serves as a vital sanctuary for seabirds, specifically those following the Atlantic Flyway. The island is often described as “Tern City” due to the sheer density of its breeding populations during the summer months. It currently hosts approximately 40,000 nesting terns, making it a global epicenter for these species.

The island is most notable for supporting:

• Common Terns: The world’s largest breeding colony of this species.
• Roseate Terns: The largest colony of these federally endangered birds in the Western Hemisphere, with roughly 5,000 nesting individuals.

A Military Past: The Era of Fort Michie

The island’s landscape was not always a haven for wildlife. In the late 19th century, tern populations were decimated by the millinery trade’s plume hunters and the onset of military development. In 1897, the U.S. Army acquired the island to construct Fort Michie as part of the Coast Defenses of Long Island Sound.

Operational from the Spanish-American War through World War II, the base transformed the island’s natural composition of sand and rubble. The Army paved over the terrain to build concrete fortifications and permanent gun emplacements, including one of the largest gun installations in the United States—a 16-inch gun on a disappearing carriage. To protect the coast, the shoreline was armored with massive granite rocks.

The Great Gull Island Project and Restoration

The transition from a military site back to a natural ecosystem began on March 31, 1949, when the American Museum of Natural History acquired the island. Under the leadership of Dr. Helen Hays, the museum launched the Great Gull Island Project, a long-term effort to restore the landscape so that terns could return and thrive.

This initiative has turned the island into the longest-running seabird research station in the U.S., boasting more than 55 years of recorded data. Beyond research, the site provides essential field training for hundreds of young scientists and employs volunteers to monitor nests and maintain the habitat.

Current Threats and Conservation Goals

Despite its success as a conservation story, Great Gull Island faces significant environmental pressures. Researchers and the Great Gull Island team are currently working to address several critical threats:

• Climate Change: Rising sea levels and warming waters threaten the stability of the nesting grounds.
• Physical Decay: Crumbling Army structures and ongoing erosion jeopardize the island’s integrity.
• Global Responsibility: Because Roseate Terns are endangered in both the U.S. And Brazil (where they winter), maintaining this specific population is considered a global priority.

Key Takeaways

• Location: A 17-acre island in Suffolk County, NY, located 0.4 miles southwest of Little Gull Island.
• Biodiversity: Home to the world’s largest Common Tern colony and the Western Hemisphere’s largest Roseate Tern colony.
• History: Former site of Fort Michie (1897–1949), featuring a massive 16-inch gun installation.
• Management: Owned and restored by the American Museum of Natural History since 1949.

Frequently Asked Questions

Who owns Great Gull Island?

The island is owned by the American Museum of Natural History, which acquired the property in 1949 to restore its ecosystem.

Why are Roseate Terns important?

Roseate Terns are federally endangered. Great Gull Island provides a critical breeding ground for approximately 5,000 of these birds, making it a cornerstone of their survival in the Western Hemisphere.

What was the military purpose of the island?

The island housed Fort Michie, which served as part of the Coast Defenses of Long Island Sound to guard the entrance to the sound from the Spanish-American War through World War II.