Forster’s Tern
Forster's Tern
Sterna forsteri
At a Glance
Several of the terns are very similar in appearance. Forster's Tern looks so much like a Common Tern that it was largely overlooked by 探花精选 and other pioneer birders. However, Forster's is more of a marsh bird at most seasons, especially in summer, when it often nests on top of muskrat houses. Unlike Common Tern, Forster's regularly winters along our southern coasts.
All bird guide text and rangemaps adapted from by Kenn Kaufman漏 1996, used by permission of Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Category
Gull-like Birds, Gulls and Terns
IUCN Status
Least Concern
Habitat
Coasts and Shorelines, Freshwater Wetlands, Lakes, Ponds, and Rivers, Saltwater Wetlands
Region
California, Eastern Canada, Florida, Great Lakes, Mid Atlantic, New England, Northwest, Plains, Rocky Mountains, Southeast, Southwest, Texas, Western Canada
Behavior
Direct Flight, Flap/Glide
Population
150.000
Range & Identification
Migration & Range Maps
Much less migratory than Common Tern, wintering regularly along southern coastlines of United States.
Description
14-15" (36-38 cm). W. 30 (76 cm). Like other medium-sized terns, has long forked tail, black cap in breeding season. Summer adults have pale silvery upperside of wingtips; base of bill orange. Young and winter adults mostly white-headed with bold black ear patches, not connecting across nape as on other terns.
Size
About the size of a Crow
Color
Black, Gray, Orange, White
Wing Shape
Broad, Long, Pointed, Tapered
Tail Shape
Forked, Long, Notched
Songs and Calls
Harsh nasal beep.
Call Pattern
Falling, Flat
Call Type
Chirp/Chip, Rattle, Raucous, Scream
Habitat
Marshes (fresh or salt), lakes, bays, beaches. During summer is mostly around marshes, either coastal salt marsh or large marshy lakes in the interior. May visit any waters during migration. Winters mostly along coast, especially around estuaries, inlets, coastal lagoons, sheltered bays.
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Behavior
Eggs
3, sometimes 1-4. Olive to buff, variably marked with brown. Incubation is by both sexes, 23-25 days.
Young
Both parents feed young in nest. Development of young and age at first flight not well known.
Feeding Behavior
Forages by flying and hovering over water, plunging to take fish from just below surface. Also may dip down in flight to take items from surface, and will forage in the air, catching insects in flight.
Diet
Fish, insects, other small aquatic life. Diet is mostly fish at all seasons, but in summer on marshes may eat many insects. Also eats small crustaceans, frogs.
Nesting
May breed in loose colonies, with spacing dictated by arrangement of good nesting sites. Sometimes associated with colonies of Yellow-headed Blackbird. Aggressive toward other birds in vicinity of nest. Nest site is in marsh, on top of dense vegetation or mats of floating dead plants, often on top of muskrat house. Sometimes placed on ground near marsh, or on abandoned nest of grebe. Where it nests in same marsh as Black Tern, Forster's tends to choose higher and drier nest sites. Nest (built by both sexes) is platform of reeds and grasses, with deep hollow at center lined with finer material and shells.
Climate Vulnerability
Conservation Status
Has declined in some areas with loss or degradation of marsh habitat. Recreational boating on nesting lakes may have impact as well, since wakes from speedboats often flood nests.
Climate Threats Facing the Forster's Tern
Choose a temperature scenario below to see which threats will affect this species as warming increases. The same climate change-driven threats that put birds at risk will affect other wildlife and people, too.