Bird populations improve after Elwha Dam removals

When officials breached two major dams along the Elwha River, scientists immediately began studying how salmon would respond. Collectively, it was the largest dam removal in U.S. history and migratory fish including coho, Chinook and steelhead had been unable to swim the river for 100 years.

With both dams gone by 2014, salmon quickly began making their way upstream. Their return was hailed as a breakthrough for ecosystem recovery, but salmon weren’t the only species that benefited. While birds never had much difficulty making it over the dams, they had also suffered. Studies showed that less prey availability from fewer fish in the river had meant less nesting success and survivability. Fewer salmon meant fewer birds. Now scientists wondered if the birds would come back too.

To uncover bird responses to this enormous, ecosystemic change along the Elwha, Ph.D. student Ethan Duvall of Cornell University and Dr. John McLaughlin of Western Washington University are using conceptual models to forecast population shifts.

They have been looking at earlier abundance and distribution data, collected before the dams were removed, and then surveying birds along the river. Although it’s still early in the restoration process, they say, their results are encouraging. “The American dipper, for example, is now abundant in areas which they were not previously prior to dam removal,” Duvall says. Not only have the early successional species—like the spotted sandpiper—shown impressive increases in abundance, but river birds have been even more adaptable than predicted. This indicates, Duvall concludes, “that the ecosystem as a whole is responding positively to the dam removals.”

Not all species are showing immediate progress. Common Mergansers, for instance, rely on mature forest and a diet of fish, so they’ll likely take decades—or even a century—to respond to these slow-moving habitat changes. Others, like spotted sandpipers, have responded more quickly because they eat a variety of species such as macroinvertebrates that are more available along the shoreline.

The scientists now hope their findings at the Elwha will be useful for studying the ecological effects of other dam removals. Birds, with their variety of nesting needs, foraging strategies, diets, and habitat niches, are often used as bioindicators. Not only are birds relatively easy to detect and monitor, the scientists say, but they also show swift responses to habitat restoration that point to large-scale changes.

That appears to be the case in the Elwha River where slowly but surely, the birds are returning home.

This article was inspired by findings presented at the 2022 Salish Sea Ecosystem Conference.