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The Ivory Bill·Birds·Seabirds

Forster’s Tern, Sterna forsteri

Forster's terns resting on a beach.

Forster’s Terns are medium-sized seabirds that breed in freshwater and brackish marshes in North America, particularly in the central United States, the Gulf Coast, and the Atlantic coast, from May to July.

Forster’s Terns are commonly found in large marshes with dense vegetation, such as cattails and bulrushes, where small fish and aquatic invertebrates are abundant during the breeding season. These habitats provide ample nesting sites and foraging opportunities.

They forage in shallow waters, estuaries, and along the edges of lakes and rivers for small fish, including minnows and silversides, and aquatic invertebrates such as shrimp and crayfish. They may also feed on insects, such as dragonflies and beetles, and occasionally on crustaceans.

Forster’s Terns exhibit specialized foraging techniques, including hovering and diving to capture fish near the water’s surface. They have keen eyesight to detect prey from above and can adjust their flight patterns to exploit different prey types effectively.

Courtship involves elaborate displays where males present fish to females as a courtship offering. Aerial displays include synchronized flying, high-speed chases, and mutual calling. These displays reinforce pair bonds and signal readiness for nesting.

Nest building is a collaborative effort by both parents, who construct floating platform nests from reeds, grasses, and other plant materials. Nests are typically anchored to emergent vegetation in shallow water to protect against predators and fluctuating water levels.

Egg laying occurs from late May to early June, with the female usually laying two to three eggs. Both parents share incubation duties, which last about 23 to 25 days. Upon hatching, the chicks are semi-precocial and require significant parental care. Initial diets for chicks consist of regurgitated small fish and aquatic invertebrates provided by the parents.

Chicks learn to forage by observing and following their parents. They face vulnerabilities such as predation by larger birds, mammals, and adverse weather conditions. Parental care includes leading chicks to foraging areas, protecting them from predators, and teaching them to capture and handle different prey.

Chick fledging occurs about 28 to 35 days after hatching, with continued guidance from adults as the chicks develop their foraging skills. Their diet evolves to include a wider range of fish and invertebrates as they grow and become more proficient at hunting.

Forster’s Terns undertake migratory journeys, leaving their breeding grounds in late August to early September. They follow specific flyways, traveling through the central United States and along the coasts to reach wintering regions along the Gulf Coast, the Caribbean, and Central America.

Wintering habitats include coastal bays, estuaries, and offshore waters, where they forage for small fish, shrimp, and other marine invertebrates. Their diet during winter is diverse, adapting to the availability of food in these coastal and marine environments.

Forster’s Terns typically leave their wintering grounds in late February to early March, returning north to their breeding areas as temperatures rise and food becomes more abundant, ensuring a rich supply of prey for the breeding season.