About this time each year, as I scan any gathering of gulls resting near the shore in Alameda, I suddenly stop. Why does that mid-sized gull look grey, rather than white or smudged brown? And why does it have a small red bill with a black tip? Oh, I remember our post-breeding visitors, Heermann’s Gulls. While they may spend several fall and winter months on California’s northern coast, most of that time they are fishing in the first few miles of the Pacific Ocean, where we don’t see them. Occasionally a few come into the Bay and stop along our shoreline or elsewhere in the East Bay.

When they are breeding in the Gulf of Mexico, Heermann’s Gulls have a white head, grey belly and black back but when they travel north after breeding, their heads have more grey feathers (I don’t think they work any harder raising their young than do other species of gulls). When we see them, the adult’s back, breast and belly are also grey, its wingtips and tail are black and its legs blackish, so its red bill gives it a dapper look.

Heermann’s Gulls start to breed when they are four years old. While the vast majority nest on a single island in the Gulf of Mexico, some now nest in Seaside (Monterey County) and on Alcatraz Island. Like many islands, their nesting island attracted rats, which seriously threatened the gulls’ survival, but a massive extermination effort has removed the rats and the gulls are doing well. Indeed, some ornithologists think the Heermann’s Gulls have expanded to new nesting locations because their Gulf of Mexico island is now getting too crowded. Their nesting success each year depends on the availability of fish, shrimp, and insects small enough to feed the tiny chicks, which means they need unpolluted waters near their island, and of course lots of fish off the northern California coast in the fall and winter before they return to the Gulf of Mexico to nest in the spring.

For a nest, the female Heermann’s Gull makes a small scrape on the ground, usually in a bare or almost bare area, then adds a few twigs and feathers. She lays two or three eggs that are splotched with browns and beige, to meld with the color of the ground beneath the eggs. Both parents incubate the eggs for about 20 days and care for the chicks for about two weeks. Because of the hot climate, down-covered new-born chicks need shade for the first few days; they can die if left unsheltered for more than an hour or so. As the chicks get older, they cluster in groups cared for by fewer adults, but their parents continue to feed them. Adults and chicks eat fish, crabs, shrimp, lizards and insects. Adult Heermann’s Gulls also use another method to get food — they follow fishing Brown Pelicans, swooping in as a pelican pulls up from a fishing dive to steal the pelican’s catch.

Heermann’s Gulls were named after a nineteenth century doctor, naturalist and explorer, Adolphous Heermann, who collected some of them as specimens, along with other birds, animals and plants throughout the western United States. In addition to the gull, both another animal and a plant were originally named after Heermann.

The next time you see gulls perched at the shore, look carefully for a mid-sized gull with a grey belly, darker grey back, and a red bill; if you find one, you will be seeing one of our fall visitors, a Heermann’s Gull.

Marjorie Powell is a member of the Golden Gate Audubon Society and its Alameda conservation committee, Friends of the Alameda Wildlife Reserve.