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Contact information
For information on Wisconsin's rare vertebrate animals, contact:
Rich Staffen
Conservation Biologist
For information on Wisconsin's rare invertebrates, contact:
Jay Watson
Conservation Biologist

Forster's Tern (Sterna forsteri)



Forster's Tern (Sterna forsteri), listed as Endangered in Wisconsin, prefers large semi-permanent and permanently flooded wetlands that support extensive growths of cattail and hardstem bulrush. The required avoidance period is May 15 - July 15.

State status

Status and Natural Heritage Inventory documented occurrences in Wisconsin

The table below provides information about the protected status - both state and federal - and the rank (S and G Ranks) for Forster's Tern (Sterna forsteri). See the Working List Key for more information about abbreviations. Counties shaded blue have documented occurrences for this species in the Wisconsin Natural Heritage Inventory database. The map is provided as a general reference of where occurrences of this species meet NHI data standards and is not meant as a comprehensive map of all observations.

Note: Species recently added to the NHI Working List may temporarily have blank occurrence maps.

Documented locations of Sterna forsteri in the Natural Heritage Inventory Database as of July 2015.
Summary Information
State StatusEND
Federal Status in Wisconsinnone
State RankS1B
Global RankG5
Tracked by NHIY

Species guidance

Forster's Tern (Sterna forsteri) has very few known occurrences in the state and is of the highest priority for conservation; we encourage you to consult with your District Ecologist or an NHI Zoologist for specific recommendations for your site.

Note: a species guidance document is not available at this time. Information below was compiled from publication ER-091.

Identification: Distinguished from common tern by orange bill and legs, silvery white tips of upper wing surface, and white edge on outer tail feathers.

Habitat: Large marshes, estuaries, and lake islands are common breeding habitats.

State Distribution: Uncommon migrant and uncommon summer resident. Lakes and large marshes in the lower Green Bay area, Lake Winnebago area and surrounding lakes, and the Mississippi River. Nesting colonies most common in lower Green Bay, Lake Puckaway (Green Lake County), and Lake Poygan and Rush Lake (Winnebago County). A map outlining Pre-1977 and 1997 to Present Distribution is available.

Diet: Small fish and insects.

Clutch: Nest at 4 years of age.3 brown or olive eggs with dark brown dots or scrawled lines; laid from June to July.

Incubation: 24 days. Fledging occurs at about 4 weeks of age.

Nest: Constructed from marsh vegetation.

Management Guidelines: Loss of nesting habitat due to high water levels, lake shore development, carp activity, and wetland filling is a key concern. Natural marsh conditions should by maintained and restored on larger inland lakes to provide potential nesting habitat. The creation of artificial nesting islands and platforms have successfully increased the number of acceptable nesting sites. Human access to colonies and nesting sites should be limited.



Forster's Tern

Photo © Lee Karney.

Forster's Tern

Forster's Terns nest in productive emergent marshes with open water nearby, where the terns forage for small fish and invertebrates.

Photo © Len Blumin.

Wildlife Action Plan

Wisconsin Wildlife Action Plan graphic

Natural community (habitat) associations

The table below lists the natural communities that are associated with Forster's Tern. Only natural communities for which Forster's Tern is "high" (score=3) or "moderate" (score=2) associated are shown. See the key to association scores for complete definitions. Please see the Wildlife Action Plan to learn how this information was developed.

Ecological landscape associations

The table below lists the ecological landscape association scores for Forster's Tern. The scores correspond to the map (3=High, 2=Moderate, 1=Low, 0=None). For more information, please see the Wildlife Action Plan.

This map shows the probability of Forster's Tern occurring in each of Wisconsin's Ecological Landscapes.  Actual scores can be found in the table to the left.

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Landscape-Community combinations of highest ecological priority*

Ecological priorities are the combinations of natural communities and ecological landscapes that provide Wisconsin's best opportunities to conserve important habitats for a given Species of Greatest Conservation Need. The 10 highest scoring combinations are considered ecological priorities and are listed below. More than 10 combinations are listed if multiple combinations tied for 10th place. For more information, please see the Wildlife Action Plan.

* Ecological priority score is a relative measure that is not meant for comparison between species. This score does not consider socio-economical factors that may dictate protection and/or management priorities differently than those determined solely by ecological analysis. Further, a low ecological priority score does not imply that management or preservation should not occur on a site if there are important reasons for doing so locally.

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Issues/threats and conservation actions

Conservation actions respond to issues or threats, which adversely affect species of greatest conservation need (SGCN) or their habitats. Besides actions such as restoring wetlands or planting resilient tree species in northern communities, research, surveys and monitoring are also among conservation actions described in the WWAP because lack of information can threaten our ability to successfully preserve and care for natural resources.

Threats/issues and conservations actions for rare animals

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Last revised: Thursday, December 22, 2022