Record Bald Eagle Numbers In North Idaho (And Biologists Don’t Know Why)

Every winter, hundreds of bald eagles migrate through Idaho’s panhandle. They stop at Lake Coeur D’Alene to feed on kokanee salmon for a few weeks. And this year, the number of eagles are at a record high.

Migrating eagles start to arrive in mid-November, just as the blue-backed kokanee salmon return to the lake.

Carrie Hugo is a wildlife biologist with the Bureau of Land Management. She has been counting bald eagles of all ages at Lake Coeur d’Alene for the last eight years. This year Hugo has counted more than ever.

“The highest count this year on December 20 was 383,” she said. “For our area, the highest count prior to that was 272 in 2010.” 

So, why are so many eagles coming to Lake Coeur d’Alene this year? Hugo said it’s a mystery.

“Honestly, I can’t answer it,” she said.

One of the things she’s been wondering—have the eagles been breeding more successfully in recent years?

“If there was a bunch of juveniles, then you’d just think, ok, we’ve had four years of really good nesting, but there’s not really a difference in the ratio between adults and juveniles,” Hugo said.

She also has wondered if the weather this fall in Alaska and Canada where the eagles migrate from could have been a factor.

“They were here earlier in big numbers, so I don’t know if there was some sort of cold snap up north that would make them come down in larger numbers,” Hugo said.

Eagle watchers on the west side of Washington state, in Skagit county, where migrating eagles also stop over, didn’t see as many this year. Hugo said it’s not clear if more eagles simply came further east.

Or, could it be that there were more salmon in the lake? Idaho’s Department of Fish and Game does annual trawling surveys to count the number of kokanee, but those data haven’t been analyzed and biologists are skeptical about directly linking the number of fish to the number of birds in any single year.

Hugo will keep count of the eagles at Lake Coeur d’Alene until the end of the month.