Prior to the 1930s, gulls in northwest Spain inhabited beaches alongside human settlements. But as hungry people started gathering huge amounts of eggs, beachside turf was no longer a safe place for the gulls to nest and raise their young. The gulls flocked to remote seaside cliffs. Then, in the 1960s, when Spain opened a series of landfills near the gulls’ secluded habitat, the sudden food bonanza sent these nesting colonies into a decades-long boom. 

The gulls’ fortunes changed again in the 1990s when the landfills closed. Without enough food to support the inflated populations, gull numbers dropped. And it’s this stress, Martínez-Abraín thinks, that spurred the gulls to begin returning to long-abandoned nesting sites, including on human-accessible islets and even inside cities. To Martínez-Abraín, this is a perfect example of refuge abandonment. With the threat of egg harvesting long ended, the gulls are reclaiming their former beach habitat. 

Plus, now that these new gull colonies are established, they’re drawing in other seabirds, Martínez-Abraín says. Many birds like to nest near other birds, so much so that researchers regularly use decoys to draw real birds to new locales. So far, Martínez-Abraín and his colleagues have documented egrets and oystercatchers moving in to join the gulls on the beach. The newcomers, he says, take the gulls’ success as a sign that these habitats are once again safe for breeding.

“When you’re looking for a bar at night to have supper, you first check whether the bar already has people eating or not,” Martínez-Abraín says. “The birds do exactly the same thing.”

Whether the gulls can hold on to their new turf, however, is still up in the air. People in Spain aren’t typically eating gull eggs anymore, but many people in Spain do view gulls as pests, says Neeltje Boogert, an animal behavior expert at the University of Exeter in the United Kingdom who studies conflict between gulls and humans. 

“As soon as wildlife is in our habitats in a way that disturbs us, we don’t actually want that,” Boogert says.

Martínez-Abraín knows that not everyone likes gulls. “They come to playgrounds and eat the sandwiches of the children, or they defecate in the fancy boats of rich people,” he admits.

But as humans become more urbanized, and as people continue to reframe their relationships with wild animals, he says to expect more species abandoning refuge habitats for new—or perhaps old—terrain.

“It’s a new scenario of coexistence between humans and wildlife,” he says.