Forster’s Terns are often mistaken for Common Terns because they have the same coloring during the breeding season but have longer tails and a black eye ring during the non-breeding season.
Breeding adult Forster’s Terns have black caps, black-tipped orange bills, white underparts, pale gray upperparts, and red legs.
Non-breeding adult Forster’s Terns lose the black caps and instead, only a black eyepatch remains. The rest of their heads and their underparts are white and their bills are now totally black. Their wings appear silvery with a hint of black tips on their primaries.
Juvenile Forster’s Terns have brown and gray heads, backs, and wings. They have distinct black eyepatches and black bills. Their underparts are white and their legs are red.
- Sterna forsteri
- Length: 13.0 – 14.2 in (33 – 36 cm)
- Weight: 4.6 – 6.7 oz (130 – 190 g)
- Wingspan: 30.7 -31.5 in (78 – 80 cm)
Forster’s Terns breed in northern North America and spend winter in the south. Some remain all year in southern US states.
Habitat And Diet
You can find Forster’s Terns in colonies of freshwater and saltwater marshes with open water and available floating vegetation during the breeding season. When they migrate, they are often in oceans, bays, and estuaries near the coast.
Forster’s Terns hunt for small fish from the air. They can dive into deep water, sometimes submerging their whole bodies. They may also wait for the tide to come in around mudflats so they have better access to the small fish, crustaceans, and frogs in shallow water. They also eat insects that they pick off from the water or capture while in flight.
Forster’s Tern Calls:
Nests of Forster’s Terns may be on the ground near marshes, built on top of dense vegetation, or floating dead plants. Both male and female adults build the nests out of reeds and grasses and line them with softer material and shells. The female lays one to four eggs and both parents take turns in incubating them for a period of twenty-three to twenty-five days.
Forster’s Terns are named after naturalist Johann Reinhold Forster.
Forster’s Terns aggressively defend their colonies when a predator is detected. This behavior also benefits other birds sharing their nesting sites and other birds may also join in defending against predators.