Arguably the Gulf of California's only endemic seabird species, the Yellow- footed Gull is large and white-headed, with a dark slate-gray mantle and bulbous bill that recalls the Western Gull (Larus occidentalis). Indeed, until recently the Yellow-footed Gull was treated as a subspecies of Western Gull, but it is probably more closely related to the Kelp Gull (L. dominicanus) of the Southern Hemisphere.
Although its breeding range lies completely within Mexico, the Yellow-footed Gull occurs regularly in the United States as a postbreeding visitor to the Salton Sea in southeastern California. The species first appears at this location in late May, with its numbers building there to many hundreds by July and August and then tapering off through the fall.
The status of this species as a Gulf of California endemic has made it the focus of conservation efforts (its population is smaller than that of any other North American gull). How-ever, much remains to be learned about its biology. Despite detailed studies of its breeding biology, plumage variation, and vocalizations, little is known of its feeding ecology, niche requirements for foraging, control and physiology of dispersal, and population status. In these details, the Yellow-footed Gull remains poorly known compared to other large gulls in North America, and further studies are needed. The Yellow-footed Gull is a model species for a cost-benefit analysis of colonial nesting.