The Washington Post article Drunk birds are causing havoc in a Minnesota town. Police say they’ll sober up soon. describes birds becoming intoxicated after eating berries:

“The Gilbert Police Department has received several reports of birds that appear to be ‘under the influence’ flying into windows, cars and acting confused,” Police Chief Ty Techar wrote in a statement Tuesday. An early frost meant that berries had fermented earlier than usual, he explained, and birds were eating them and getting drunk.

Incidents around town involving intoxicated birds appear to be more prevalent than in past years, Techar added, because many have not yet migrated south. “It appears that some birds are getting a little more ‘tipsy’ than normal,” he wrote. “Generally, younger birds’ livers cannot handle the toxins as efficiently as more mature birds.”

A few supporting videos:

Is the fermentation happening to the berries while on the tree or on the ground as the police suggest, or is it really after being ingested by the birds? How is an anaerobic environment produced for fermentation into alcohol but not subsequent conversion to vinegar?

Humans are a clever species, on par with some birds. They are known to collect the berries and ferment them first before ingesting, and will forage for a trap to let gas escape but keep the oxygen out. Have birds found a better way?

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1 Answer 1


The insides of fruits are relatively anaerobic environments. Natural fermentation, as in berries that get birds intoxicated, is primarily from yeast, and it seems most likely that humans recognized this process before intentionally encouraging fermentation of anything. Natural fermentation reaching high ethanol concentrations occurs especially when berries high in sugar are frozen and then thawed.

Dudley, R. (2004). Ethanol, fruit ripening, and the historical origins of human alcoholism in primate frugivory. Integrative and comparative biology, 44(4), 315-323.

Fitzgerald, S. D., Sullivan, J. M., & Everson, R. J. (1990). Suspected ethanol toxicosis in two wild cedar waxwings. Avian Diseases, 488-490.

  • $\begingroup$ Interesting! I usually think of the inside of fruit as sterile, but maybe that's not exactly the case. Sounds like the basis of a new question! $\endgroup$
    – uhoh
    Commented Jan 22, 2019 at 3:06

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