Forster's Tern

Sterna forsteri

Order CHARADRIIFORMES - Family LARIDAE - Subfamily Sterninae

Menu

1. Cool Facts
2. Description
3. Sound
4. Range
5. Habitat
6. Food
7. Behavior
8. Reproduction
9. Conservation Status
10. Other Names

One of several medium-sized terns that appear similar in appearance, the Forster's Tern breeds primarily in marshes and winters along the coasts. The comma-shaped black ear patch in winter plumage is distinctive, but some other plumages are very confusing.

Cool Facts

• Forster's Tern is the only tern restricted almost entirely to North America throughout the year.

• Spawning common carp are so vigorous that they can dislodge Forster's Tern eggs from floating nests.

• Forster's and Black terns breed near each other in marshes. Wandering semi-precocial young may account for observations of each species feeding the other's young.

Description

• Size: 33-36 cm (13-14 in)
• Weight: 130-190 g (4.59-6.71 ounces)

• A medium-sized tern.
• White with black cap.
• Tail long and deeply forked.
• Wings very white in most plumages.
• Legs orange and relatively long.

Breeding Adult (Alternate Plumage): Plumage mostly immaculate white. Black cap down to and including the eye. Bill orange with black tip. Wings and mantle pale gray. Flight feathers pale silvery-gray, usually lighter than mantle, except for darker tips to outermost primaries. Tail light gray, deeply forked with white outer edge.
Adult winter (Basic Plumage): Black cap lost. Curved black mask covering eye and ear region, not extending onto back of neck. Crown and forehead white. Bill black. Feet dusky orange.
Wear and molt results in gradations between these two plumages, with varying degrees of smudginess on nape and worn, dark primaries.

Sex Differences

Sexes look alike.

Immature

Immature resembles winter adult, but has even darker primaries. May have dark centers to tertials.

Sound

Common call a descending "kerrr." Threat call a harsh "zaar."

»listen to songs of this species

Range

Summer Range

Breeds at scattered locations throughout North America. Largest area of breeding on freshwater lakes and marshes across south-central Canada and north-central United States. Also in the Great Basin, locally in California, around the western Great Lakes, and locations along the Atlantic and Gulf coasts.

Winter Range

Winters along California, Gulf, and lower Atlantic coasts. Also in smaller numbers inland from the upper Gulf Coast and in Central America.

Habitat

• Breeds in marshes, generally with lots of open water and large stands of island-like vegetation.
• Winters in marshes, coastal beaches, lakes, and rivers.

Food

Small fish and arthropods.

Behavior

Foraging

Plunges into water from flight; may hover briefly before plunging.

Reproduction

Nest Type

Varies from unlined scrape in mud or sand, to elaborate raft of floating vegetation, or on top of a muskrat lodge. Typically placed in clumps of marsh vegetation close to open water.

Egg Description

Olive to buff, marked with numerous small spots and blotches of dark brown, often concentrated around the larger end.

Clutch Size

Usually 2-3 eggs. Range: 1-6.

Condition at Hatching

Downy, eyes open, able to walk but stays in nest.

Conservation Status

Species of special concern in the Midwestern states because of declines resulting from loss of wetland habitat.

Other Names

Sterne de Forster (French)
Gaviote de Forster, Charran de Forster (Spanish)

Sources used to construct this page:

McNicholl, M. K., P. E. Lowther, and J. A. Hall. 2001. Forster's Tern (Sterna forsteri). In The Birds of North America, No. 595 (A. Poole and F. Gill, eds.). The Birds of North America, Inc., Philadelphia, PA.