Forster's TernSterna forsteriOù et quand les observer

Forster’s Tern combines a pale body, pointed wings and a deeply forked tail with an aerial hunting style. Cornell describes a marsh-breeding species that uses many kinds of wetlands during migration. The registered Columbia opportunity is specifically Umatilla National Wildlife Refuge and the John Day pool near Boardman–Irrigon, not the entire river. Source: https://www.allaboutbirds.org/guide/Forsters_Tern/lifehistory

Size

Species-specific body-length measurement not verified.

Weight

Species-specific weight not verified.

Lifespan

Species-specific lifespan not verified.

Status

A current formal global conservation assessment was not verified.

A hunting bird patrols above the water, adjusts its flight and plunges after small prey. Cornell reports that some dives submerge the entire body, although feeding is often near the surface. Between feeding bouts, birds may rest together. Colonies can shift as water levels, predators and disturbance alter the suitability of marsh nesting sites.

• It plunge-dives for small fish.
• Some feeding dives submerge the whole bird.
• Breeding adults have a black cap.
• Nonbreeding adults have a dark eye patch.
• The tail is deeply forked.
• Marsh nesting sites can change with water levels.

The registry characterises terns as principally warm-season targets but supplies no species-specific month boundaries. A retrieved Umatilla bird list includes a dated Forster’s Tern observation; a single dated observation cannot define a recurring season. No local recurring numerical calendar was verified, and the location months therefore remain empty.

Cornell identifies freshwater, brackish and saltwater marshes as breeding habitat, with open water and relatively predator-free nesting places. At Umatilla, river-influenced sloughs and wetlands beside John Day pool are the relevant habitat mosaic. An exposed main-channel view and a sheltered refuge slough offer quite different observation conditions.

Small fish dominate the diet described by Cornell. The birds locate prey from the air and plunge into the water, sometimes becoming fully submerged. This differs from the underwater pursuit used by grebes and cormorants. Specific fish species and feeding success at Boardman–Irrigon were not verified.

Common name

Forster's Tern

Scientific name

Sterna forsteri

Animal group

Birds

Size

Species-specific body-length measurement not verified.

Weight

Species-specific weight not verified.

Lifespan

Species-specific lifespan not verified.

Status

A current formal global conservation assessment was not verified.

Identification

Breeding adults have a black cap and black-tipped orange bill. Outside breeding plumage, an isolated dark eye patch and pale nape are useful features. Cornell notes pale primaries, white underparts and a long forked tail. Separate similar terns using the complete combination rather than bill colour alone. https://www.allaboutbirds.org/guide/Forsters_Tern/id