Forster's Tern

Overview

Forster's tern (Sterna forsteri) is a medium-sized seabird in the family Laridae that breeds in marshes across North America. It is classified as Least Concern on the IUCN Red List, though it faces threats from habitat degradation and water pollution in certain regions.

Identification

• Size and build: Medium-small tern, 33–36 cm long, with a slender body and deeply forked tail.
• Breeding plumage: Intense black cap extending down the neck, pale grey upperparts, bright white underparts, and a black-tipped orange bill with bright orange legs.
• Non-breeding plumage: White crown with a distinctive black comma-shaped patch covering the eye and ear-covert; bill is black and legs are dull brownish red.
• Flight: Often hovers with head pointing downward before initiating a shallow, headfirst plunge-dive with wings partially folded backward.

Habitat

This species is primarily found in marshes, estuaries, and shallow open water, utilising both freshwater and saltwater environments. It breeds in North America, ranging from the Atlantic and Pacific coasts to the Prairies and Great Lakes, and winters in the southern United States, Mexico, the Caribbean, and northern Central America.

Diet

The diet consists mainly of fish such as carp, minnows, sunfish, and herring, supplemented by insects like dragonflies and grasshoppers, as well as crustaceans and amphibians. It forages by plunge-diving for fish in shallow water or hawking for insects, often preferring turbid water where prey density is higher.

Did you know?

Forster's terns exhibit intense colonial aggression, mobbing nest predators with loud calls and dives, which can provide protective benefits to nearby species such as ducks, grebes, and yellow-headed blackbirds that share the nesting sites.