WatchList Species Account for Thayer’s Gull (Larus thayeri)

Qualifies for the list as a Declining Yellow List Species

 

Photo: Don Roberson
Photo: Don Roberson

Formerly considered a subspecies of the Herring Gull and sometimes of the Iceland Gull, the Thayer’s Gull is a medium-sized white-headed gull that breeds on islands and peninsulas of the Canadian Arctic and in northwestern Greenland. During non-breeding, it is found on the West Coast from British Colombia south to central Baja California and is observed casually to the east and throughout the interior.

 

A near-shore species, it frequents bays and sounds, lagoons, the mouths of rivers, tidal flats and shores, but also visits garbage dumps. It nests on cliffs on arctic islands. In ecology it is similar to the Herring Gull. It feeds on the surface of the water, especially the tidal zone at ebb tide, on beaches, around bays and harbors and boats, where its main foods are invertebrates (mollusks, crustaceans and marine worms), fish, carrion, garbage, and occasionally the eggs and young of other birds.

 

There is no reliable information on long-term population trends, a situation aggravated by the fact that this species is sometimes difficult to distinguish from the Iceland and Herring gulls. The bird suffers predation on eggs, chicks and occasionally adults from Gyrfalcons and Arctic Foxes. Estimates of the total population puts it at around 12,000 individuals, but this figure may be low, since many breeding colonies of the bird are presumed to be still unknown. Though individual colonies are subject to human disturbance, the majority are inaccessible and the bird is not thought to be endangered or threatened.