Guide to North American Birds
Conservation status Overall population probably stable, perhaps increasing slightly; range has expanded recently to include southern Alaska.
Family Gulls and Terns
Habitat Large lakes, coastal waters, beaches, bays. Found on both fresh and salt water, favoring protected waters such as bays, lagoons, rivers, lakes, not usually foraging over open sea. Inland, more likely on large lakes than on small ponds. Nests on open ground on islands, coasts.
The largest of the terns, larger than many gulls. Cosmopolitan, nesting on five continents. In North America, it is common along both coasts and locally inland, mainly around large bodies of water. Noted for its long adolescence, with the young dependent on their parents for many months; even in late winter, many an adult Caspian is trailed by a begging youngster from the previous nesting season.

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Feeding Behavior

When foraging flies high over water, hovers, then plunges to catch fish below surface. Less often flies low, dips down to catch prey at water's surface. May steal food from other birds.


Eggs

1-3, rarely 4 or 5. Pale buff, spotted with brown or black. Incubation is by both parents (female may do more), 20-22 days. Young: May leave nest a few days after hatching, move to nearby shore. If colony is undisturbed, young may remain at nest until ready to fly. Both parents bring food for young. Age at first flight about 30-35 days; young may remain with parents as long as 8 months.


Young

May leave nest a few days after hatching, move to nearby shore. If colony is undisturbed, young may remain at nest until ready to fly. Both parents bring food for young. Age at first flight about 30-35 days; young may remain with parents as long as 8 months.

Diet

Mostly fish. Often concentrates on a few abundant fish species in a given locale (for example, shiner perch on California coast, alewife on Great Lakes). Also eats insects, sometimes eggs or young of other birds.


Nesting

First breeds at age of 3 years. Nests in colonies, sometimes in isolated pairs. Male may fly low over colony carrying fish; female follows. On ground, courtship feeding (male feeds female). Nest site is on bare ground, among driftwood or debris, perhaps sometimes on floating mats of dead vegetation. Nest (built by both sexes) is shallow depression, sometimes with rim or lining of debris.

Illustration © David Allen Sibley.
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Text © Kenn Kaufman, adapted from
Lives of North American Birds

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Migration

Inland breeders move to coast and southward for winter. Some winter south to West Indies, northern South America.

  • All Seasons - Common
  • All Seasons - Uncommon
  • Breeding - Common
  • Breeding - Uncommon
  • Winter - Common
  • Winter - Uncommon
  • Migration - Common
  • Migration - Uncommon

See a fully interactive migration map for this species on the Bird Migration Explorer.

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Songs and Calls

Low harsh kraa. Also a shorter kow.
Audio © Lang Elliott, Bob McGuire, Kevin Colver, Martyn Stewart and others.
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