Tivoli Bays Wildlife Management Area
Red Hook, New York
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The Hudson River Estuary extends from New York Harbor 150 miles north to the Federal Dam at Troy. Oceanic tides ranging between three and six feet rise and fall twice a day throughout the estuary. In the lower Hudson fresh water from the surrounding countryside mixes with salt water from the Atlantic Ocean, but at Tivoli Bays the river's tidewaters are entirely fresh.


The Tivoli Bays is part of the Hudson River National Estuarine Research Reserve, managed as a field laboratory for research and education about the Hudson River Estuary. The New York State Department Of Environmental Conservation also operates the site as a wildlife management area.

Tivoli Bay Map
Click image for larger map
The Tivoli Bays is a large freshwater tidal wetland surrounded by undeveloped land. The average tidal range at the bays is about four feet. The property includes:
  • Tivoli North Bay, a cattail marsh cut by a network of winding tidal creeks and pools;

  • Tivoli South Bay, a shallow wetland cove with mud flats exposed.at low.tide;

  • Cruger, South Cruger, and Magdalen islands and the adjacent near shore shallows;. Uplands, about acres of woods and fields;

  • Stony Creek and the Saw Kill, shallow, fast-flowing streams that empty into the bays.
In 1850 the New York Central Railroad laid tracks on an embankment at the western edge of the bays. Two bridge openings in North Bay and three in South Bay allow water to enter and leave with each tidal cycle. This reduced both river access and water exchanges to a fraction Of what they had been. Sediments in the bays have been accumulating at an accelerated rate since then, speeding, the evolution of the bays from deep water to wetland.


Narrow-leaved cattail is the most common plant of the freshwater tidal marsh in Tivoli North Bay. Muskrats build their lodges out of cattail and feed on its roots and young shoots. Birds such as Virginia rails, red-winged blackbirds, marsh wrens and least bitterns nest in the wetlands. Spatterdock, wild rice and invasive plants such as purple loosestrife and common reed also grow in North Bay and provide food and nesting opportunities for other species.

In the winter ice scours the wetlands and shorelines. The dead cattail stalks, wild rice, spatterdock, pockerel weed and other marsh plants are swept under water where they decay and add nutrients to the Hudson River food web. Occasionally bald eagles scavenge water around the bays. As soon as the ice is out, kingfish and megansers return to fish in the open waters.

Spring brings new life to the bays. Migrating ducks, shorebirds, and ospreys feed and rest in the bays before continuing their flight north. American toads, spotted salamanders, and green frogs breed in shallow pools on Cruger Island. Bright yellow blossoms of marsh marigolds brighten the swampy areas.

In early summer snapping turtles leave tidal creeks to lay eggs in dry soils adjacent to the marsh. Noisy splashes signal carp spawning in the bays. Male fourspine stickleback fish build cup shaped nests of plant material amidst the underwater plant life.

During the summer Tivoli South Bay is covered by Eurasian water chestnut, a floating plant introduced from Asia that shelters a rich aquatic insect community. Hard black seed pods with sharp spikes that wash up along the Hudson's shore are evidence of this plant's invasion of the estuary. Like zebra mussels, another recently introduced species, water chestnut has profoundly changed the estuarine ecosystem.

Fall brings sky-darkening flocks of red-winged blackbirds, starlings, grackles and cowbirds that arrive at dusk to roost in the cattail marsh and the wooded tidal swamps between the bays. Rafts of migrating waterfowl signal a temporary lull in the cycle of life at the Tivoli Bays.

Hudson River Tide Charts

Hudsonia Limited

Hudsonia is an organization for research, public education, and technical assistance in the environmental sciences. Projects emphasize ecology and field biology, science in the service of planning and conservation, and pure research. Many Bard undergraduate and graduate students have participated in Hudsonia programs as interns, assistants, co-investigators, or thesis candidates. Hudsonia equipment and library are available to the college communities.
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Hudson River National Estuarine Research Reserve

The Hudson River National Estuarine Research Reserve (HRNERR) is a network of four coastal wetlands located along 100 miles of the Hudson Estuary. The primary goal of the Reserve is the protection and prudent management of the Reserve's biologically diverse estuarine communities. The sites are managed as long-term natural field laboratories for research and education.

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Page Updated February 2000