Elegant terns are suddenly all over San Francisco shores

Royal. Sandwich. Caspian. Elegant. These are the colorful names for different species of terns, some of San Francisco Bay’s most graceful seabirds. 

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A wave of elegant terns — identifiable by their tangerine bills, black head feathers and ash-white bodies — flooded Crissy Marsh in San Francisco this week.  

Around this time of year, the birds have migrated north into California to prey on fish like anchovy.

“They are a highly social bird, and it’s very fun to watch them interact with each other and other bird species when they’re in large groups!” Phoebe Parker-Shames, wildlife ecologist for the Presidio Trust, told SFGATE in an email. “This season, I noticed some birds facing each other and flicking their heads up, which apparently may be a threat or vaguely aggressive behavior. Considering I haven’t ever seen it escalate into anything, I’d call it more like a grumpy hello.”

Parker-Shames encouraged residents to visit Crissy Marsh, a 20-acre restored wetland in the Presidio, to catch the elegant terns before they move on. In a post on social media, the Presidio wrote, “The Elegant Terns have returned to Crissy Marsh and if you know, you know. If you don’t, this is your sign to find out.”

Elegant terns — which the International Union for Conservation of Nature lists as near threatened — have expanded the places they breed and generally multiplied in California over time. About 50 years ago, the species would only breed in the Gulf of California, primarily on one island called Isla Rasa, according to Peter Pyle, a staff biologist at the Institute for Bird Populations. Every summer, they would follow the anchovy as far as the Bay Area and, during El Niño years, often farther north. 

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“Then some 40-50 years ago, they started expanding northwards as breeders,” Pyle said in an email to SFGATE. “… Over the past 15 years, numbers in spring gradually increased, and they were confirmed breeding in the South Bay about 10 years ago. I’m unsure if they are breeding elsewhere around here now, but numbers keep expanding in spring, [including] hundreds or even a thousand or so this past April to May in SF Bay.”

Depending on the time of year, several other species of terns — including Caspian terns, California least terns, Forster’s terns and Arctic terns — can appear in the Bay Area.

Scientists expect that this year’s El Niño, which forecasters on Thursday gave a 75% of reaching historic strength as soon as October, could push the elegant terns past California northward along the West Coast. 

“In El Niño years, they’ll often go farther north, following the warmer waters,” Jack Dumbacher, the ornithology curator for the California Academy of Sciences, told SFGATE. “It will be interesting to see how far north they go for food enjoying the warm water.”