Introduction: Distribution and Population
Most people describe terns as graceful long-winged birds and often refer to them as sea swallows for their graceful nature. There exists 42 species of terns in the world and can be found on both sides of the Atlantic and throughout temperate Eurasia but it is absent from the Pacific side of North America (Hosking, 1984).
Two species of terns , the Caspian Terns (Sterna caspia) and the Common Terns (Sterna hirundo) can be found nesting in Hamilton Harbour around the Windmere Basin area and Eastport Piers 26 and 27.
When the breeding season is over and winter arrives, the Common Terns migrate to areas such as to southern Baja California, South Carolina and even to southern Africa (Godfrey, 1966). The Caspian Terns can be found wintering in central California, Baja California, the Gulf of Mexico and the West Indies (Figure 2)(Godfrey, 1966).
The Caspian Terns have done well in this area whereas the Common Terns have been experiencing long-term population declines. Between 1975 to 1994, the number of nests for the Caspian Terns increased from 0 to 313 nests (Moore et al., 1995). In contrast, the number of nests for the Common Terns have recently declined from 1 028 nests in 1990 to 868 nests in 1994 (Moore et al., 1995).
The main reason for the decline in Common Terns is competition for nesting substrate with the Ring- billed Gulls (Larus delawarensis). In November 1994, wildlife islands were constructed in the northwest corner of Hamilton Harbour nearby Eastport. The purpose of the islands is to create a sheltered region for new fish habitat but will also serve as a new nesting site for colonial waterbirds such as the Common and Caspian Terns that were nesting on the mainland, south of these islands (Morris, 1994). To learn more about these management efforts, please click here.
This web page will provide basic information about the biology of the Common Tern. For more information on the following, please click on the appropriate item:
General Characteristics