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.