Gull identification is challenging. As the birds age over their first two to four years of life (depending on the species), their plumage changes in stages from mottled brown to crisp gray and white. Smaller species of gulls develop more quickly (2 to 3 years), while the larger species take four years. This free color downloadable guide will help you identify the nine most common gulls on the California coast.
Gull identification tips
- If you find a flock of mixed species, you can compare size between individuals. Size is difficult to gauge on a single bird.
- Note the shades of gray. Western Gulls have dark backs, other species are lighter. As you scan across a group of gulls look for birds with a different gray to find a new species.
- Some species of gulls hybridise. A Western may mate with a Glaucous-winged Gull and produce offspring with a mantle that is somewhere between the dark and the light of the two parents. If this bird mates with another Western gull, the offspring will be a little darker . If it mates with a Glaucous-winged Gull the offspring will be a little lighter. Thus you can get a range of grays and other characteristics in these hybrid groups.
- Pay attention to leg, eye, and bill color.
- Bill proportions change between species. For instance, the Western Gull has a massive beak, the California Gull has a long beak, and the Mew Gull has a delicate beak.
- Bill proportions and the prominence of a ridge by the eye gives each species a unique “expression”. Western and Glaucous-winged Gulls look angry. Mew gulls look cute.