Dead birds were intoxicated, an investigation finds
Young blackbirds found dead at a primary school in Cumbria suffered from alcohol poisoning, according to an investigation.
Animal health specialists were called to examine a dozen birds found in the playground, many with trauma injuries.
Post-mortem analysis revealed that one of the birds had a large amount of pure alcohol in its liver.
Scientists suggest the birds sustained their injuries in flight because they were intoxicated by fermented berries.
Staff from the Animal Health and Veterinary Laboratories Agency (AHVLA) published their results in the Veterinary Record.
A local wildlife sanctuary cared for a further bird found in the area, which they described as unsteady on its feet, using its wings to support itself and leaning on the walls of its enclosure.
Under the influence
The bird made a full recovery and was released after two weeks of care.Trouble brewing
When AHVLA researchers analysed the dead blackbirds they found all the birds had eaten berries from a nearby rowan tree.
Tim Harrison, development officer of the British Trust for Ornithology's (BTO) Garden BirdWatch explained: "Generally speaking, birds that have a lot of fruit in their diet are more efficient at metabolising alcohol and are better adapted at eating fruit that has higher alcohol concentrations."
He continued: "There are anecdotal reports of birds acting 'drunk' but these tend to be very rare".
But damaged berries were also recorded on the ground where the birds were discovered.
Scientists explained that the berries on the ground were damaged and would have been vulnerable to yeast infestation. This would have precipitated fermentation and subsequent alcohol production.
According to Paul Duff and colleagues at the AHVLA, who carried out the post-mortem analysis on the dead blackbirds, the berries found in the birds' guts smelled of fermentation - the chemical process of sugars breaking down into alcohol.
Tissue samples sent for analysis partially confirmed the scientists' suspicions when one revealed high concentrations of ethanol, pure alcohol, in the liver of an affected bird.
However, alcohol was not identified in the toxicology tests of two other samples.
A similar diagnosis was made in 1999 for a group of redwings, which had been feeding on holly berries that were fermenting following a frost.