Illustration © David Allen Sibley.
Learn more about these drawings.
Text © Kenn Kaufman, adapted from
Lives of North American Birds
Photo: Patty McGann/Flickr Creative Commons
Forster's Tern
Sterna forsteri
| 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. |
|---|---|
| Family | Gulls and Terns |
| 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. |
Photo Gallery
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.
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.
Young
Both parents feed young in nest. Development of young and age at first flight not well known.
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.
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- All Seasons - Common
- All Seasons - Uncommon
- Breeding - Common
- Breeding - Uncommon
- Winter - Common
- Winter - Uncommon
- Migration - Common
- Migration - Uncommon
Songs and Calls
Harsh nasal beep.How climate change could affect this bird's range
In the broadest and most detailed study of its kind, Audubon scientists have used hundreds of thousands of citizen-science observations and sophisticated climate models to predict how birds in the U.S. and Canada will react to climate change.
Read more: climate.audubon.org
Each map is a visual guide to where a particular bird species may find the climate conditions it needs to survive in the future. We call this the bird’s “climatic range.”
The colors indicate the season in which the bird may find suitable conditions— blue for winter, yellow for summer (breeding), and green for where they overlap (indicating their presence year-round).
The darker the shaded area, the more likely it is the bird species will find suitable climate conditions to survive there.
The outline of the approximate current range for each season remains fixed in each frame, allowing you to compare how the range will expand, contract, or shift in the future.
The first frame of the animation shows where the bird can find a suitable climate today (based on data from 2000). The next three frames predict where this bird’s suitable climate may shift in the future—one frame each for 2020, 2050, and 2080.
You can play or pause the animation with the orange button in the lower left, or select an individual frame to study by clicking on its year.
