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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

Caspian Tern (Hydroprogne caspia)



Caspian Tern (Hydroprogne caspia), listed as Endangered in Wisconsin, prefers undeveloped sand beaches and islands along the Great Lakes, typically on sandy or gravelly coastal islands. The required avoidance period is May 20 - July 31.

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 Caspian Tern (Hydroprogne caspia). 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 Hydroprogne caspia in the Natural Heritage Inventory Database as of July 2015.
Summary Information
State StatusEND
Federal Status in Wisconsinnone
State RankS1B,S2N
Global RankG5
Tracked by NHIY

Species guidance

Caspian Tern (Hydroprogne caspia) 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: This white gull-sized tern has a black cap, coral-red bill, black legs and feet, and short, slightly forked tail. Is easily distinguished from other tern species by their greater size, thicker bill, and low-pitched, harsh calls.

Habitat: Nest on open, unvegetated islands.

State Distribution: Common migrant north and east, uncommon summer resident east. Occur during spring and summer along the shoreline of Lake Michigan and Lake Superior.

Diet: Plunge-dive for small fish. Also feed from surface, sometimes eating eggs or young of other birds.

Clutch: Caspians nest at 2-3 years of age.2-3 grayish or buffy eggs with irregular spots; laid from May to July.

Incubation: 20-22 days. Young fledge at 28-35 days old. One young typically fledges from a successful nest.

Nest: Eggs laid in shallow depressions in the ground or in nests lined with grasses, seaweeds, or mosses.

Management Guidelines: Colony instability, poor reproduction, and the low number of nesting pairs have contributed to its endangered status. Declining nesting success and colony abandonment may be due to the effects of chemical contaminants, human disturbance at colony sites, competition for nesting sites with Ring-billed Gulls and Herring Gulls, and predation by Great Horned Owls and other predators. Conservation measures include controlling public access to the nesting colonies to minimize disturbance, eliminating predators from colony sites, and monitoring all potential nesting habitat, especially dredge spoil islands.



Caspian Tern

Photo © Lee Karney.

Caspian Tern

Caspian Tern chicks in nest

Photo © Donna Dewhurst.

Caspian Tern

Photo © Donna Dewhurst.

Caspian Tern

Caspian Tern occurs on Lower Green Bay and along the Lake Michigan shore.

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 Caspian Tern. Only natural communities for which Caspian 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.

Natural community Score
Great Lakes Beach 3
Lake Michigan 3
Lake Superior 3

Ecological landscape associations

The table below lists the ecological landscape association scores for Caspian 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 Caspian 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