Curious Alaska: Hold my berry — are Bohemian waxwings getting drunk on fermented fruit?

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Question: Swarms of Bohemian waxwings just swooped in and cleaned out every single berry from the two mountain ash trees in our yard. We’ve always heard that the berries ferment and the waxwings get drunk from eating them. Is that true? (We’ve had waxwings crash into our windows in the past but we’re not sure that proves anything.) Thanks.

The evidence for Bohemian waxwing intoxication is somewhat circumstantial but quite plentiful. And while it’s likely the birds get tipsy from eating fermented berries, sober birds smack into windows too.

Bohemian waxwings are a wintertime fixture in Anchorage, darting in large flocks from one berry-filled tree to another. The city is studded with ornamental berry trees like mountain ash, and as temperatures turn cold, sugars in those berries ferment, said Rick Sinnott, a retired Alaska Department of Fish and Game wildlife biologist.

The waxwings eat every berry they can find, essentially working their way through the city’s berry supply.

“I don’t think they eat fermented berries on purpose — like people go to the bar — but that’s what is there,” Sinnott said.

He likened the search for winter berries to arriving at a grocery store only to find beer and whiskey.

“It just interacts with their physiology and causes them to be a little goofy, lose orientation, stuff like that, when they fly,” Sinnott said.

But even “perfectly sober birds” may fly into windows fairly regularly, Sinnott said.

Anchorage Bird Treatment and Learning Center, a local bird rehabilitation organization, has received around six Bohemian waxwings that struck windows since November. It’s hard to say whether they were drunk — by the time they arrive at the center, the birds are already acting stunned or concussed, having just hit their heads, said Katie Thorman, wildlife rehabilitation assistant.

But the center can’t rule out intoxication, either.

“Unless there’s a way I can test their blood alcohol or breathalyze them — maybe someday,” Thorman said.

Sulli Gibson, a serious birder who manages birding and photography tours on St. Paul Island in summer, said that waxwings, including their Cedar waxwing and Japanese waxwing cousins, eat a lot of fruit year-round, which makes them especially susceptible to intoxication. But waxwings have adapted. They have more alcohol-processing enzymes and their livers are even relatively large compared to other avians.

“Which helps them probably combat getting drunk more than say, like, another bird that eats just fruit a little bit,” Gibson said. “But still, if they eat enough, they do get drunk. And it does happen.”

Over the past 40 or 50 years, urban beautification efforts and ornamental tree promotion to attract birds mean that Anchorage has thousands of mountain ash trees, said Sinnott, the biologist.

Animals that avoid crowded Anchorage in the summer make their way into town during the winter months because of the city’s plentiful food options. The usually people-averse ravens seek out the city’s prolific garbage where they can select “the juiciest, fattiest things,” Sinnott said.

And moose head into town too, avoiding deep snow in the mountains and finding crab apples that plunk down along Anchorage streets. Those can also ferment, a situation that led to Anchorage’s perhaps most famous intoxicated animal, Buzzwinkle. The moose was spotted in 2007 with holiday lights tangled in his antlers at Bernie’s Bungalow Lounge downtown, after likely feasting on fermented crab apples.

In a 2013 column remembering the moose, Sinnott wrote, “He was blotto, and he knew it. Too large to fit in a taxi, we left him to sleep it off in the fenced courtyard.”

Meanwhile, across the Canadian border near Whitehorse, Yukon, Maria Hallock with Yukon Wildlife Preserve said the organization treats four to six Bohemian waxwings each spring because of what she called “ethanol-induced ataxia from berries.” It tends to happen after a long stretch of warm weather, she said.

They keep the birds in a small, quiet space for at least 24 hours, depending on the severity of their injury — most birds are usually picked up after colliding with a window or car.

“We usually stock up our freezer on ripe berries in the late fall to feed these patients,” Hallock wrote in an email.

In the Lower 48, the Cedar waxwing is also known to consume a few too many fermented berries every so often.

In Portland, Oregon, Stephanie Herman — a wildlife rehabilitator with Portland Audubon who spends her days caring for injured, orphaned and displaced wild animals — said few animals get drunk on fermented berries since that is essentially spoiled fruit. But the group has seen Cedar waxwings they suspect have grown intoxicated from the berries.

She also said some birds are brought in that have injuries, which may also cause them to act strangely. It can be hard to tell the difference between a bird with a concussion or a brain injury and a bird that’s under the influence.

“Intoxication isn’t all that common. I think people hear it and it sticks in their brain,” Herman said. “But it’s much more common for us to be seeing trauma-related neurological symptoms. But that said, we do think we’ve seen plenty of intoxicated patients over the many years that we’ve been operating.”

The good news is that drunk birds can recover fairly quickly. After an initial exam, the birds are treated with fluids and sometimes heat, and away from people, Herman said.

Getting inebriated is far from the biggest issue facing Anchorage’s waxwings. Invasive starlings, bigger and more aggressive than the waxwing, continue to grow in population, which could potentially push out the Bohemian waxwing in Anchorage, Sinnott said.

“The number of starlings has just gone up,” Sinnott said. “If they keep doing that, then at some point, we’re certainly going to see less waxwings.”