Field Guide to Birds of North America
Forster's Tern
General
Forster's Tern: Medium-sized tern with pale gray upperparts, black cap, and white underparts. Bill is orange with black tip. Wings are pale gray with paler primaries. Tail is pale gray and deeply forked with dark inner edge and white outer edge. Legs and feet are orange. Sexes are similar. Winter adult lacks black cap but has distinctive black eye patch, gray streaks on head, dark bill, and dull orange legs and feet. Juvnile resembles winter adult but has brown markings on back, nape, head, and upperwings that fade and orange-based black bill that darkens by end of summer.
Range and Habitat
Forster's Tern: Breeds along the Atlantic coast from Massachusetts to Texas and in interior Alberta and California east to the Great Lakes. Spends winters along the coasts from California and Virginia southward. In the west, prefers freshwater marshes, whereas in the east, prefers salt marshes.
Listen to Call
Voice Text
"ki-arr", "za-a-ap", "zrurrr", "beep"
Interesting Facts
Forster's Tern is the only tern restricted almost entirely to North America throughout the year.
They breed in marshes near Black Terns. Wandering semi-precocial young may account for observations of each species feeding the other's young.
This bird is named after the naturalist Johann Reinhold Forster.
A group of terns are collectively known as a "ternery" or a "U" of terns.
Author
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Family
Tern (Laridae)_blue
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Species
Sterna forsteri
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Length14 - 15
Inches
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Wingspan30.5
Inches
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Forster's Tern
Forster's Tern: Medium tern, pale gray upperparts, black cap, white underparts. Bill is orange, black tip. Wings are pale gray with paler primaries. Tail is pale gray, deeply forked with dark inner edge, white outer edge. Orange legs, feet. Hovers above water before diving for prey.
● Song: "ki-arr", "za-a-ap", "zrurrr", "beep"
● Foraging & Feeding: Forster's Tern: Diet consists mostly of fish, but also eats insects, small crustaceans, mollusks, frogs, and tadpoles. Catches fish at surface or by plunge diving into water from a perch or a hover; catches insects on the wing or on the water surface; reportedly eats dead fish and frogs exposed by receding ice; occasionally eats bird eggs.
● Breeding & nesting: Forster's Tern: One to four olive or buff eggs with brown or olive marks are laid on a large platform of dead grass, lined with finer grass, and usually built on a mass of dead marsh vegetation. Incubation ranges from 23 to 25 days and is carried out by both parents.
● Similar species: Forster's Tern: Common and Arctic terns have dark outer and white inner tail edges.
Flight Pattern
Shallow slow graceful flight.
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BreedingMonogamous, Loose colonies
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PopulationDeclining
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MigrationMigratory
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Weight5.6
Ounces
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