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Heermann's Gull | Larus heermanni
Heermanns meeuw | Gaviota ploma
Heermann's Gull is a dark grey gull with a red bill that breeds almost entirely in the guide area. Most of the world population nests on a single small island in the Gulf of California, Isla Rasa. After the breeding season much of the population moves north along the coast to California and beyond, in the opposite direction to most birds migrating in autumn.
Voice
A high, whining whee-ee and a nasal, repeated ka-ka-ka; in the colonies a constant din.
Recording: Isain Contreras Rodríguez — CC BY-NC-SA 4.0 · converted to mono · xeno-canto
Identification
46–53 cm, a medium-sized gull with a dark grey body, a blackish tail with a narrow white tip and a white trailing edge to the wing. Adults have a red bill with a black tip and black legs. In breeding plumage the head is bright white; outside the breeding season the head is streaked grey. Juveniles are plain dark chocolate brown with pale fringes to the upperpart feathers and a pink bill with a black tip. Adult plumage is reached in the fourth year.
Confusion species
Grey Gull Leucophaeus modestus, a vagrant in the south of the guide area, is also grey but has a black bill and a grey tail with a black band. Juvenile Laughing Gulls Leucophaeus atricilla are smaller, with a black bill, a white rump and a white tail with a black terminal band. Juvenile Yellow-footed Gulls Larus livens and Western Gulls Larus occidentalis are larger, with a heavier bill and a mottled brown plumage.
Habitat
Coasts and inshore waters: beaches, rocky shores, harbours and piers, and bare islets for breeding. It catches its own fish but also often steals fish from Brown Pelicans and other seabirds.
Where the bird is most at home, classified by the vegetation units of Mexico and Central America.
Range and movements
Breeds on islands in the Gulf of California, by far the most on Isla Rasa, and in small numbers elsewhere along the coast of Baja California and western Mexico. Outside the breeding season along the Pacific coast from Baja California to Nayarit and Jalisco, scarcer south to Guerrero and Oaxaca, with single records in Central America. Outside the guide area much of the population moves after breeding to the coasts of California, Oregon and Washington.
- Resident
- dark = core range, pale = thinly spread
How and when to look
Harbours and beaches around the Gulf of California, such as at Guaymas, Bahía de los Ángeles and La Paz, offer the best chance all year. The combination of a dark grey body and a red bill is unique among the gulls of the guide area.
Conservation status
Near Threatened. Because almost the whole population breeds on one island, the species is vulnerable to disturbance, introduced predators and changes in food supply at sea, especially of sardines and anchovies. Isla Rasa is protected, and breeding success has improved since rats and mice were removed.
Scientific name
Larus heermanni | Cassin, 1852
Cassin described the species in 1852 and placed it straight away in the genus where it still stands. The genus Larus was introduced in 1758 by Linnaeus. Larus is Latin, from Ancient Greek laros, and appears to have referred to a gull or another large seabird. heermanni honours the American physician and naturalist Adolphus Lewis Heermann (c. 1821–1865), who collected in California. The specimen the first description was based on came from San Diego, California.