Prall's Island Heron Nesting Enhancement Feasibility Study

Case Name:


United States of America

Restoration Types:

Population Support


Affected DOI Resources:

Migratory Birds


Staten Island



Project Description

Prall's Island is an 89-acre island in the Arthur Kill between Linden, NJ and Staten Island, NY. Originally known as Dongan’s (and later Duncan's) Island, the island became a major agricultural center in the 1800s when the marshes were diked to farm salt hay. During the 1930s, dredge spoils from the Arthur Kill Channel were deposited on Prall's Island, expanding it to its current size. Between World War I and II, the U.S. Navy maintained a "mothball" fleet of surplus ships in the waters off Prall's Island. Ideas were proposed to develop the island in the 1970s until bird watchers and ornithologists began to recognize the islands significance as breeding habitat for migratory birds. A variety of wading birds, including black-crowned night herons, yellow-crowned night herons, little blue herons, great egrets, snowy egrets, and glossy ibises, were observed in large numbers on the island in 1978, and further studies found that they had began to use the island as a rookery. In 1984, the island was transferred to the New York City Department of Parks and Recreation (NYC Parks), and it has since been managed as a wildlife refuge to protect the "Harbor Herons" and other birds. In 1990, Prall's Island was heavily oiled due to the Exxon Bayway oil spill, causing extensive losses of salt marsh vegetation on the island and adjacent shorelines. Over the next several years, nesting activity declined on Prall's Island and the Harbor Herons began to breed on other islands in the NY-NJ Harbor Estuary. To examine the cause of the nesting colony collapse and identify potential restoration opportunities, funds from the Exxon Bayway oil spill settlement were provided to the NYC Parks Natural Resources Group (NRG) to conduct an extensive study on colonial wading bird nesting habitat on Prall's Island. The NRG documented the presence of mammalian predators on the island, and catalogued over 7,000 trees to assess nesting habitat and locate suitable areas to install nest platforms. The NRG also collaborated with the New York City Audubon Society (NYC Audubon) to monitor how the Harbor Herons use the island, and the U.S. Department of Agriculture's (USDA) National Resources Conservation Service (NRCS) to assess soil structure and chemistry. With the data collected from the study, it was determined that the spread of invasive plants such as tree-of-heaven, mile-a-minute, and glossy buckthorn had an adverse effect on the complex species interactions on the island. It is believed that this likely contributed to the decline in wading birds nesting on Prall's Island.

Restoration Land Ownership

County or Municipal

Parties Implementing Restoration

Natural Resource Conservation Service; New York City Audubon Society; New York City Department of Parks & Recreation

DOI Project Representatives

Fish and Wildlife Service

Restoration Documents

Document NameDocument Date
No records to display.

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