Fermented Berries Embolden Birds

Fermented Berries Embolden Birds

During the first frost, berries that remain on the tree will ferment producing alcohol held within the sweet fruits. When birds feed on fermented winter berries they can become intoxicated. And recent research indicates they may be getting more drunk than first thought. While most birds may get slightly tipsy from ingesting fermented berries and could not be identified as drunk by the average person, there are some that seem to overindulge.

Bohemian waxwing perched in a European mountain ash whose fermented berries landed a flock of the birds in a Canadian animal health clinic earlier this fall.

Bohemian waxwing perched in a European mountain ash whose fermented berries landed a flock of the birds in a Canadian animal health clinic earlier this fall.

This was apparently the case with a group of bohemian waxwings (Bombycilla garrulus) found in Whitehorse in the Yukon Territory of Canada. Earlier this fall the birds flew in and went on a bender with berries from a European mountain ash (Sorbus aucuparia).  This feathered friends ended up in the drunk tank at Yukon’s animal health unit; a wildlife facility outfitted with cages similar to rodent enclosures ready and awaiting birds who have gorged on alcoholic berries. These birds must have seriously overdone it as they were visibly impaired; they were groggy, had juice-stained beaks and were patently incoordinated, walking or flying. The birds are examined for other illnesses which could explain their symptoms, but nothing else could be confirmed. The bohemian waxwings will recover within a few hours, except those unfortunate few who perish in building or car collisions due to the incoordination.

Many anecdotal reports of empirical evidence of drunken flocks of birds have been cited across North America and Europe, but few actual research studies exist with confirmed data points. This may be due to the lack of a routine test for alcohol poisoning in animals, and tests that are available are very expensive and can be inconclusive; alcohol poisoning doesn’t leave any characteristic lesions and alcohol disappears relatively quickly. Veterinary scientist, Paul Duff, with the United Kingdom’s Animal and Plant Health Agency assisted a police investigation into the suspicious death of 12  common blackbirds (Turdus merula) found at an elementary school in Cumbria County. The postmortem report indicated these birds had succumbed to alcohol poisoning after ingesting fermented berries from the European ash tree. These results were arrived at based on significant levels of alcohol observed in the liver sample. A similar diagnosis was arrived at by the same agency for a group of redwings (Turdus iliacus) who had sustained fatal falls after indulging on fermented holly berries.

Waxwings, seemingly, have a pretty high tolerance for alcohol due to their relatively large livers, which is lucky because they depend on the berries to help them through harsh winters. Immature birds may not fare as well when subjected to a diet of fermented berries, possibly adults learn how to identify and avoid toxic berries. Intoxication seems to be more dangerous to those birds which congregate in urban; navigating infrastructure, architecture and hard surfaces pose innate danger to birds who may not be able to fly straight. If you find a bird which appears to be drunk but uninjured, carefully place it in a box with holes cut out for air and call your town’s animal control officer or transport it to the local wildlife refuge for treatment and rehabilitation.