Dam removal benefits for birds

Well, some birds anyway. Birds that eat fish that are impacted by dams.

This is another bit of news related to the Elwha River, and how its damming, and now freedom, is affecting the surrounding ecosystem. The article concerns itself with a small, round, very cute bird called a dipper. They’re neat birds to watch, if you are so lucky as to see one. They’re quite active, and named for their habit of submerging themselves underwater to find food – which includes small fish, such as juvenile salmon.

According to studies of dippers in the Elwha River area, populations of the birds that were on the dammed side of the river showed poorer population and individual health, apparently due to the lack of tiny salmon in their diets:

Tonra and his colleagues worked along four streams, three of which were blocked to salmon either by waterfalls or dams. They banded the birds, weighed them and collected blood samples. They looked at carbon and nitrogen in the birds’ blood to determine their level of marine-derived nutrient intake.

The research team watched for multiple attempts to breed and an inclination to stay in the nesting area year-round, and tracked what type of food was delivered to nestlings.

The birds with salmon access had more marine-derived nutrients and were 20 times more likely to attempt multiple broods. They were 13 times more likely to stay year-round and had an annual adult survival rate that was 11 percent higher than their salmon-deprived peers.

. . .

“Within the same river you basically have two different populations,” Tonra said.

There’s good news in the team’s second dipper study, published in the December 2015 issue of the journal Biological Conservation: Within a year of the Elwha Dam removal, Tonra and his colleagues were able to document an increase in salmon-derived nutrients in American dippers.

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About Fjothr Lokakvan

More or less Northern Tradition polytheist.
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