Avian biologists say they’ve seen a peculiar development with American white pelicans along the Lower Columbia River — new colonies.

American white pelicans, with 9-foot, black-tipped wings and long orange beaks, are typically migratory birds. The birds’ numbers in the region dropped in the 19th and 20th centuries. But in recent years, they’ve been overwintering around the Columbia River, and they’ve set up at least two colonies that are now home to thousands of breeding pairs.

James Lawonn, avian biologist with the Oregon Department of Fish and Wildlife, told OPB’s “Think Out Loud” that the pelican colonies have formed and grown as a result of two different kinds of environmental changes.

Climate change is bringing more drought to the American West, and that’s led pelican colonies to fail or struggle in places like Utah’s Great Salt Lake and Eastern Oregon. At the same time, habitat restoration efforts along the Columbia River have brought back habitat destroyed in previous centuries.

“These are birds that can easily move across the landscape. Flight doesn’t cost much, energetically, for them,” Lawonn said. So when large numbers of birds showed up in the Columbia River estuary in 2022 and 2023, “That was potentially related to the failure at the Great Salt Lake colony and colonies in Oregon, such as the one on Malheur Lake.”

Meanwhile, habitat restoration efforts have brought new islands to the Lower Columbia River. Those sites are harder for predators like coyotes to access, and so offer protections to pelican chicks. They also provide easy access to food for adult birds that eat 4 pounds of fish per day.

And as environmental changes have affected where white pelicans choose to nest, the birds themselves are changing the environment at their new homes.

“Mostly the pelican diet is composed of fish that are not of economic importance. Common carp are a really big part of the diet, for example, in Malheur Lake and some other areas, and common carp are a non-native species. It’s great that pelicans like to eat them,” Lawonn said.

In the Columbia River, many researchers believe the birds are now feasting on American shad, another non-native species, according to a report in environmental news outlet Columbia Insight.

“But pelicans can also eat fish that biologists are really concerned about,” Lawonn said. “Some of those fish would include salmon and steelhead, that are listed under the Endangered Species Act.”

Even though white pelicans consume an enormous amount of fish — “if you’ve got a colony of 2,000 pelicans, you’re literally talking tens to hundreds of tons of fish every breeding season” — those protected salmon and steelhead are only a very small part of their diets, Lawonn said.

But a little can go a long way.

“We recently have learned that pelicans can eat adult sockeye salmon,” he said. “That can be really important from a conservation point of view, because if an adult makes it to the river, we usually expect that that adult would be able to spawn to create future generations of fish, but if pelicans eat them before they’re able to spawn, that can be a really bad thing for fish conservation.”

It’s something avian biologists and other wildlife experts will continue to monitor as they see how climate change and other environmental shifts affect white pelican populations in the years ahead.