Seagulls are by far the most common bird along the coast near Santa Cruz, California. There are dozens of different seagull species, and you need a keen eye to tell them apart. To make things even more challenging, gulls change color with age and with the season. It’s almost impossible to identify the species of a juvenile gull because they all look very similar.

Sometimes called “sky rats,” seagulls are omnivores. They are opportunistic feeders who will eat just about anything, alive or dead. They keep the beaches from piling up with rotting matter and are an important part of the marine ecosystem. The three most common gulls in the Santa Cruz area are the California gull, the western gull, and the Heermann’s gull. You might see others, too, such as the pink-footed herring gull (Larus argentatus).

California Gull

The California gull (Larus californicus) is a medium-sized gull, less than two feet long, with a wingspan of four feet. It is distinguished by its yellow bill, which has a black ring near the tip with a red spot on the underside.

This seagull ranges along the West Coast, from southern British Columbia to southern Mexico. It also goes inland as far north as northern Canada and east to North Dakota and Kansas, where it likes to breed and nest in the spring, especially on lakes. The female lays two or three eggs in a shallow depression lined with feathers and vegetation. Both parents take turns feeding the young and guarding the nest.

Western Gull

A large gull, the western gull (Larus occidentalis) is over two feet long, with a wing span of over four feet. A common sight from Canada to Mexico, they rarely go inland. If there is food available, they might stay year-round, or they might migrate south in the winter.

You can tell a western gull by its yellow bill, which has just an orange spot on the end of the lower beak (no black ring like a California gull). Although the male is larger than the female, they have similar plumage.

Colonies of nesting pairs establish a territory on an isolated island or on rocky cliffs and build nests on the ground. The female lays three eggs, and the male and female take turns incubating them for a month.

Heermann’s Gull

The Heermann’s gull (Larus heermann) is easier to identify than most gulls. It has darker, sooty-gray plumage, a white head, and a bright reddish-orange bill with a black-tipped beak. It can be confused with the parasitic jaeger (Stercorarius parasiticus) and, like the jaeger, will steal the catch of other birds.

They are coastal birds, ranging from southern British Columbia to Central Mexico. They migrate south in December. The majority (about 90%) nest on an island, Isla Rasa, in the Gulf of Mexico. They are the only gull that breeds south of the US-Mexico border.

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This piece is part of the Marine Life Guide. Download the free app with many tours of the Santa Cruz area and beyond.