New York Natural Heritage Program
Caspian Tern
Hydroprogne caspia (Pallas, 1770)

Habitat [-]
In North America, Caspian Terns breed in various types of habitats including estuaries, salt marshes, islands (coastal and freshwater), bays, and beaches. Both nesting colonies in New York are on islands in large lakes. Populations along the Great Lakes typically nest on islands and beaches with a substrate consisting of sand, pebbles, or gravel with very little vegetation. Inland populations tend to nest on the shell banks and sandy, pebbly beaches of islands in rivers or lakes. Coastal populations nest on open, sandy beaches and islands. Caspian Terns have been observed nesting near driftwood, perhaps offering shade or concealment, along shorelines in the above mentioned localities (Bent 1921, Cuthbert and Wires 1999). There are only two known breeding colonies in New York. One is on an island composed of rock located 5.5 miles from the mainland in Lake Ontario. The vegetation on the island consists of grass and weeds with sparse trees around the perimeter and a grassy meadow in the center of the island (Weseloh and Blokpoel 1993). The area where the tern's nested was described in 1986 as a firm substrate of soil and mud with some vegetation such as mustard (Cruciferae) (Weseloh and Blokpoel 1993). It was noted that the island supports a high number of nesting colonial waterbirds and appeared "saturated" with nesting gulls even prior to the tern colonization (Weseloh and Blokpoel 1993). The other nesting location in New York is an island in Lake Champlain that is covered by thick reed canary grass. The terns utilize a 0.25 acre clearing previously created and occupied by comormants (Capen pers. comm.). Caspian Terns have also utilized man-made habitats for nesting. One example is a colony in Ontario, Canada, where three islands were constructed in Hamilton Harbour to replace nesting areas that were slated for development. The islands were built to encourage Caspian Terns to nest there by forming them high enough so that the islands would not get washed over during storms, raised knolls were created, and sand and gravel was laid down as a nesting substrate. The terns successfully colonized the islands the first year they were created (Neuman and Blokpoel 1997). During migration, Caspian Terns are most often seen on large inland marshes, lakes, and rivers. Those that migrate along the Atlantic Flyway use barrier islands, beaches, and wetlands as stopover sites. Wintering areas are similar to migration habitats (Bent 1921, Cuthbert and Wires 1999).

Associated Ecological Communities [-]
  • Great Lakes dunes
    A community dominated by grasses and shrubs that occurs on active and stabilized sand dunes along the shores of the Great Lakes. Unstable dunes are sparsely vegetated, whereas the vegetation of stable dunes is more dense, and can eventually become forested.
  • Great Lakes exposed shoal
    The aquatic community of the shallow littoral zone of the Great Lakes that occurs along windswept shores that are exposed to wave action, typically associated with islands and points. The lake substrate may be sandy, gravelly, cobbly, bouldery, or with submerged bedrock outcrops.
  • Sand beach
    A sparsely vegetated community that occurs on unstable sandy shores of large freshwater lakes, where the shore is formed and continually modified by wave action and wind erosion. Characteristic species that are usually present at very low percent cover include various grasses and other herbs.

Associated Species [-]
  • Herring Gull (Larus argentatus)
  • Ring-Billed Gull (Larus delawarensis)
  • Great Black-Backed Gull (Larus marinus)
  • Common Tern (Sterna hirundo)