Robins and waxwings have been known to eat berries that can intoxicate them this time of year

FUI - "Flying under the influence"

By Colleen Cronin / ecoRI News staff

In the past few weeks, Roger and Gail Greene have started to see something a little funny through the window of their home: A flock of robins feasting on berries in their yard were stumbling around, and a few even flew into their windows.

The Greenes, who are former longtime state Department of Environmental Management employees and stewards for the conserved land near their property, thought back to the education programs on common Rhode Island birds they used to run in the 1980s and ’90s.

The robins, they thought, were probably acting that way because they were a little tipsy.

Robins, waxwings, and other birds can become intoxicated this time of year after eating fermented winter berries, according to Scott McWilliams, a professor of wildlife ecology and physiology at the University of Rhode Island.

“They’re kinda like us in that they can be made drowsy and drunk by alcohol,” McWilliams told ecoRI News.

With insects and worms pretty much gone from this area in the winter, the birds have to rely on winter berries, like those from the holly trees in the Greenes’ yard.

The combination of freezing and warming that happens this time of year causes increased sugars to build up and then ferment in the fruit still on the trees.

Just like humans, the intoxication usually isn’t bad for the birds, McWilliams said, at least in moderation.

“For us, we just fall down on the ground. For birds that fly, it can actually be catastrophic,” he said, explaining that the calls he gets this time of year about drunk birds are usually after they’ve run into something. “What happens is they lose their bearing a little bit.”

On top of the drunkenness, the berries can also cause toxicity for the birds in a different way. Holly berries, for example, have a natural toxicity that lessens but is still present in the fruit after fermentation.

For the birds to process the fruits safely, they have to take in proteins, usually from the flowers of trees, which helps to reduce the toxicity of the berries.

McWilliams said the plants develop this toxicity to help spread their seeds. (“If you make a perfect fruit, the bird is just going to come and eat the plant, poop or regurgitate the fruit and seed right there, and won’t move it around,” he said.)

While the drunkenness is mostly harmless, McWilliams acknowledged that the discombobulated birds might display some behavior that could mimic the symptoms of avian flu. But he said there are ways to tell the conditions apart.

The tipsiness is “a fairly transient thing … because the birds don’t like feeling that way either, I think,” he said, laughing a little.

The strain of avian influenza that has killed hundreds of millions of birds in the United States over the past few years causes symptoms that would last much longer, McWilliams said. “It would be a more persistent behavioral pattern that would be worrisome.”

For the moment, the Greenes are enjoying their winter neighbors — the robins are most likely birds that breed up north and come to the relatively warm climate in Rhode Island for the season, McWilliams said. Even though they have been leaving partially digested fruit on their car, the Greenes don’t mind.

As for their crash landings, “They are flying under the influence (FUI),” Roger noted.