Common Tern Habitat Model
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Draft Date:
March, 2001

Species:
Common tern, Sterna hirundo

Use of Study Area Resources:
Reproduction (winters in Florida, Central and South America)

Habitat Requirements:
Cover. Common terns nest on sandy beaches, gravelly or sparsely vegetated shores of small coastal islands, back bays, and both freshwater and salt  high marshes (Burger and Gochfeld 1991, Clapp et al 1983).  They may also nest on islands in some large lakes (Veit and Petersen 1993, DeGraaf and Rappole 1995).  Nests are on the ground, based in mats of wrack or bent-over grass stems in marshes, and sand mixed with shell hash or fine gravel on beaches (Burger and Gochfeld 1991). Common tern colonies can vary from a couple to thousands of individuals (Terres 1995). Nesting islands are usually less than 20 ha in area and close to the mainland (Burger and Gochfeld 1991). Black skimmers and roseate terns often share nesting colony sites with common terns (Burger and Gochfeld 1991).

Foraging. Terns feed by diving on schools of small fishes in shallow fresh or salt water (Terres 1995). Though common terns feed mostly on small fishes, shrimp and insects are also taken regularly, and molluscs, marine worms, spiders, tadpoles or lizards less often (Clapp et al. 1983). Food piracy is common between terns and other species (Clapp et al. 1983, Burger and Gochfeld 1991). They often feed over tide rips (typically where current flows over shallow bars), in relatively sheltered areas (Nisbet 1977). In coastal areas they feed in shallow waters offshore of beaches, inlets, or along convoluted shorelines, to about 22 km from nesting colonies, and up to 1 km from shore (Pearson 1968, Duffy 1977, Nisbet 1977, Erwin 1978). However, terns mostly feed within 6 km of colonies (Austin 1946, Pinkowski 1980).

Threats. Eggs, young, and adults are readily lost to predation by small mammals including foxes, raccoons, skunks, mink, weasels, dogs, cats, and rats, and to snakes, and a variety of birds including gulls, cervids, owls, and blackbirds (Burger and Gochfeld 1991). Human disturbance, especially in the form of intentional vandalism, also interferes with colonies (Burger and Gochfeld 1991).

Habitat Mapping:
Data Sources: Data depicting nest sites were obtained from the Maine MDIF&W Seabird Nesting Island databases, from New Hampshire Audubon Society (Diane DeLuca), and from Massachusetts Fisheries and Wildlife (Brad Blodgett).

Nesting habitats were scored according to probability of use. Recently active common tern nesting sites were scored 1.0; sites recently used by arctic or roseate terns (and so offering potential for colonization by common terns) were scored 0.5. Other sites historically used by common terns (since 1985 but no longer in use) were scored 0.4.

Feeding habitats were mapped around nesting sites currently used by common terns. These consisted of marine or estuarine open water areas within 6 km of active nesting sites, and less than 30' in depth; with this depth limitation, feeding habitats were mapped only within 1 km of shore. Since highest value feeding areas could not be distinguished from other open water areas, all feeding habitats were scored 0.3. This distinctive score also distinguishes feeding and nesting areas in the single (combined) output grid.

Sources:
Austin, O.L. 1946. The status of the Cape Cod terns in 1944: a behavior study. Bird-Banding 17:10-27.

Burger, J. and M. Gochfeld. 1991. The Common Tern: Its Breeding Biology and Social Behavior. Columbia University Press, NY. 413 p.

Clapp, R. B., D. Morgan-Jacobs and R.C. Banks. 1983. Marine Birds of the Southeastern United States and Gulf of Mexico; Part III, Charadriiformes. USFWS FWS/OBS.

DeGraaf, R.M. and J.H. Rappole. 1995. Neotropical Migratory Birds: Natural History, Distribution and Population Change. Comstock Publishing Associates, Ithaca, NY. 1995. 676 pp.

Duffy, D. 1977. Breeding populations of terns and skimmers on Long Island Sound and eastern Long island: 1972-1975. Proc. Linn. Soc. NY. 73:1-48.

Erwin, R.M. 1978. Coloniality in terns: the role of social feeding. Condor 80:211-215.

Nisbet, I.C.T. 1977. Courtship-feeding and clutch size in Common Terns. Pp.101-109 in B. Stonehouse and C. Perrins (eds.). Evolutionary ecology. (Vol. 2. Biology and environment). 310 pp.

Pearson, T.H. 1968. The feeding biology of sea-bird species breeding on the Farne Islands, Northumberland. Journal of Animal Ecology 37:521-552.

Pinkowski, B.C. 1980. Adaptations of Common Terns nesting on an inland reservoir. Prairie Nat. 12: 111-113.

Terres, J.K. 1995. The Audubon Society Encyclopedia of North American Birds. Wings Books, Avenel, NJ. 468 p.

Veit, R.R. and W.R. Petersen. 1993. Birds of Massachusetts. Massachusetts Audubon Society. 514 p.