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Photo © Ryan Brady
Common Tern (Sterna hirundo), listed as Endangered in Wisconsin, prefers the Great Lakes' shorelines, bays, sand bars of large lakes and rivers, sandy or rocky coastal islands, and marshes. The required avoidance period is May 15 - August 21.
The table below provides information about the protected status - both state and federal - and the rank (S and G Ranks) for Common Tern (Sterna hirundo). 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.
| Summary Information | |
|---|---|
| State Status | END |
| Federal Status in Wisconsin | SOC |
| State Rank | S1B,S2N |
| Global Rank | G5 |
| Tracked by NHI | Y |
| WWAP | SGCN |
Common Tern (Sterna hirundo) 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 Forster's tern by red bill and legs, darker upper wing surface and wing tips, and black outer edge on tail feathers.
Habitat: Common terns nest on isolated, sparsely vegetated islands or peninsulas in large lakes. Sandy substrates are typical.
State Distribution: Common migrant and uncommon resident north and east. Five nesting colony sites occur in Wisconsin: lower Green Bay, Lake Butte des Morts, Lake Winnebago, and Chequamegon Bay and Duluth-Superior Harbor. A map outlining Pre-1977 and 1997 to Present Distribution is available.
Diet: Primarily small fish.
Clutch: Usually nest at age 3.usually 3 olive or brown eggs; laid from late May to early June.
Incubation: 21-28 days by both parents. Fledging occurs around 28 days after hatching.
Nest: Slight depression in soil lined with grasses, seashells, or bits of seaweeds. Nest in colonies.
Management Guidelines: Habitat loss, prolonged inclement weather, nest predation, human disturbance, displacement by gull species, and possibly chemical contaminants are factors affecting nesting terns. Human disturbance near colonies during the nesting season should be prevented. Preferred nesting sites contain 10-30% vegetative cover. Sites should be managed accordingly to provide sparsely vegetated areas that are free of avian and mammalian predators, such as great horned owls, minks, rats, raccoons, and red foxes.
Click to view a larger version. Please considering donating a photo to the Natural Heritage Conservation Program for educational uses. Photo use
Photo © Lee Karney.
Several important Common Tern breeding colonies and feeding areas occur on the Great Lakes.
Photo © Len Blumin.
Photo © Naseem Reza.
Photo © Ryan Brady.
Only two Common Tern colonies occur on Lake Superior; one near Ashland, the other near Duluth-Superior.
Photo © Ryan Brady.
The table below lists the natural communities that are associated with Common Tern. Only natural communities for which Common 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 |
| Emergent Marsh | 2 |
| Floating-leaved Marsh | 2 |
The table below lists the ecological landscape association scores for Common Tern. The scores correspond to the map (3=High, 2=Moderate, 1=Low, 0=None). For more information, please see the Wildlife Action Plan.
| Ecological landscape | score |
|---|---|
| Central Lake Michigan Coastal | 3 |
| Northern Lake Michigan Coastal | 3 |
| Southeast Glacial Plains | 3 |
| Superior Coastal Plain | 3 |
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.
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.