Birds can become intoxicated from consuming naturally fermented berries and fruits, a phenomenon well-documented by wildlife officials. This occurs when high-sugar fruits are left on branches or the ground long enough for their internal chemistry to change. While the image of a drunk bird might seem humorous, the situation carries significant dangers for the involved animals. Understanding this natural process helps explain why certain birds are prone to bingeing on this boozy buffet, especially during colder months.
Fermentation The Cause of Avian Alcohol
The intoxicating substance is ethanol, the same type of alcohol found in beer and spirits. This ethanol is created through a natural biological process known as fermentation, which begins when yeast and bacteria convert the fruit’s natural sugars. Fermentation typically occurs in the late autumn and winter when fruits like berries are left on the plant past their ripe stage. The process is sped up when the fruit is bruised, which allows the ambient yeast present on the fruit’s skin to access the sugary interior.
Temperature fluctuations, specifically a freeze followed by a thaw, can concentrate the sugar within the fruit, leading to a more potent final product. This can result in alcohol levels that are surprisingly high. Birds, particularly smaller species, possess a high metabolic rate, but their livers have a limited capacity to process large amounts of ethanol quickly. This makes the birds highly susceptible to intoxication and alcohol poisoning.
Recognizing Signs of Bird Intoxication
Birds experiencing intoxication often exhibit behaviors that are noticeably uncoordinated, similar to what one might expect from a human under the influence. Obvious signs include difficulty maintaining a straight flight path, which often leads to the bird accidentally colliding with windows, buildings, or cars. These crashes are a primary cause of injury and death for intoxicated birds.
When on the ground, affected birds may stumble or stagger, finding it hard to walk or stand upright. They might display an unusual lethargy or an inability to perch properly, sometimes leaning against objects for support. These symptoms render the birds vulnerable to predators they would normally easily avoid, or to hazards like traffic.
Common Suspects Berries and Birds
The phenomenon of avian intoxication is most frequently observed in the Northern Hemisphere during late autumn and early spring. This is when the cycle of freezing and thawing creates the ideal conditions for fermentation in fruits that persist on the branch. Berries that are high in sugar and remain available throughout the winter are the most common culprits.
Specific plants known to produce these highly fermentable fruits include:
- Rowan or mountain ash
- Juniper
- Holly
- Pyracantha
- Crab apples
The birds most often involved are those that rely heavily on these persistent fruits for winter sustenance. Species frequently documented consuming these berries include:
- Cedar waxwings
- Bohemian waxwings
- European starlings
- American robins
Helping an Intoxicated Bird
The most important step upon finding a bird that appears intoxicated is to ensure its immediate safety from predators and environmental hazards. If the bird is in immediate danger, you can gently place it into a dark, quiet, and well-ventilated cardboard box. The dark, contained environment helps reduce stress and shock, which can sometimes be more dangerous than the injury itself.
It is recommended not to offer the bird any food or water directly, as an intoxicated bird may aspirate the fluid. Instead, the bird should be kept warm and left undisturbed in the box so it can metabolize the alcohol and sleep off the effects. Contact a licensed wildlife rehabilitator immediately, as they possess the specialized skills necessary for proper care and will advise on transport, ensuring the bird receives professional care and the best chance for a full recovery and release.