(Dwight, 1919, San José Island, Lower California)
Adults are similar in appearance to the Western Gull with a white head, dark, slate-colored back and wings, and a thick yellow bill. Its legs are yellow, though first winter birds do display pink legs like those of the Western Gull. It attains full plumage at three years of age.
This species is one of the largest gulls in the world, being slightly larger than the already large Western Gull. It measures 53 to 72 cm (21 to 28 in) in length and spans 140 to 160 cm (55 to 63 in) across the wings. The body mass of this species can vary from 930 to 1,500 g (2.05 to 3.3 lb). Among standard measurements, the wing chord is 40.2 to 46 cm (15.8 to 18.1 in), the bill is 5 to 6.2 cm (2.0 to 2.44 in) and the tarsus is 5.9 to 7.5 cm (2.32 to 2.95 in).
Yellow-footed Gulls are native to the Gulf of California in Mexico. Most are non-migratory, but an increasing number have been traveling to California's Salton Sea during nonbreeding periods. The population is estimated at about 60,000 and appears to be stable.
Their breeding habitat is the Gulf of California, where they nest either independently or in colonies. The birds are scavengers as well as foragers, feeding on small fish and invertebrates and preying upon seabird chicks and eggs.
- BirdLife International (2012). "Larus livens". IUCN Red List of Threatened Species. Version 2012.1. International Union for Conservation of Nature. Retrieved 16 July 2012.
- Gulls: Of North America, Europe, and Asia by Klaus Malling Olsen & Hans Larsson. Princeton University Press (2004). ISBN 978-0691119977.
- CRC Handbook of Avian Body Masses by John B. Dunning Jr. (Editor). CRC Press (1992), ISBN 978-0-8493-4258-5.
- "National Geographic" Field Guide to the Birds of North America ISBN 0-7922-6877-6
- Seabirds, an Identification Guide by Peter Harrison, (1983) ISBN 0-7470-1410-8
- Handbook of the Birds of the World Vol 3, Josep del Hoyo editor, ISBN 84-87334-10-5
- "National Audubon Society" The Sibley Guide to Birds, by David Allen Sibley, ISBN 0-679-45122-6