New York Natural Heritage Program
Black Tern
Chlidonias niger (Linnaeus, 1758)

Habitat [-]
Black Terns breed in productive freshwater marshes, typically in sites with mixtures of emergent vegetation and open water. In western New York Hickey and Malecki (1997) found that Black Terns nest primarily in sparse to moderately dense bur-reed about 26-50 cm tall in areas with a 50:50 open water/vegetation ratio, and water depths of about 50 cm. These findings were consistent with other general habitat descriptions throughout the range including in northern New York. Muskrat structures were used heavily and may reflect the vegetation type and processes that foster nest substrate formation. In marshes with less persistent emergents such as bur-reed, nest substrate formation may depend heavily on muskrat activities. Where terns nest in cattail dominated marshes, such as in northern New York (Mazzocchi et al. 1997), muskrats may not be as important since floating vegetation mats and rootstalks may form more often in marshes dominated by these more persistent emergents (also bulrushes). Exposed perches such as floating logs, fallen trees, and standing dead trees and shrubs are used as stations for resting, copulation and feeding recently fledged young (Novak 1992).

Black Terns are an area dependent species and in addition to marsh size, proximity to other wetlands is a critical factor in habitat selection. Terns favor marshes > 20 ha, but they will nest in marshes between 5-11 ha only if they are part of a larger wetland complex (Brown and Dinsmore 1984; Novak 1992). Characteristics of entire landscapes must be considered in habitat assessments because wetlands that do not correspond to landscape-scale habitat requirements may not be suitable despite favorable local conditions. Suitable nest sites occur within regenerating or degenerating wetlands where vegetation structure, rather than species of vegetation, dictates suitability (Naugle et al. 2000).

Associated Ecological Communities [-]
  • Deep emergent marsh
    A marsh community flooded by waters that are not subject to violent wave action. Water depths can range from 6 in to 6.6 ft (15 cm to 2 m). Water levels may fluctuate seasonally, but the substrate is rarely dry, and there is usually standing water in the fall.
  • Impounded marsh
    A marsh (with less than 50% cover of trees) in which the water levels have been artificially manipulated or modified, often for the purpose of improving waterfowl habitat.
  • Shallow emergent marsh
    A marsh meadow community that occurs on soils that are permanently saturated and seasonally flooded. This marsh is better drained than a deep emergent marsh; water depths may range from 6 in to 3.3 ft (15 cm to 1 m) during flood stages, but the water level usually drops by mid to late summer and the soil is exposed during an average year.

Associated Species [-]
  • American Bittern (Botaurus lentiginosus)
  • American Coot (Fulica americana)
  • Common Moorhen (Gallinula chloropus)
  • Least Bittern (Ixobrychus exilis)
  • Pied-Billed Grebe (Podilymbus podiceps)
  • Virginia Rail (Rallus limicola)