But unsteadiness on the
feet, a tendency to fall over, and losing the ability to steer is considerably
more of a problem when life is normally spent in trees or in the air.
The authors from the
Animal Health and Veterinary Laboratories Agency (AHVLA) reveal how they were
called to a primary school in Cumbria last summer after the bodies of 12 young
blackbirds were found.
A further blackbird was
discovered alive, but obviously "unwell." And two more dead birds
were subsequently found.
Foul play was suspected,
especially as some of the birds had clearly been injured. The police were
called.
Post mortem exams were
carried out on the dead birds, who were otherwise in good physical condition.
Tests to rule out lethal infections, such as avian flu, came back negative. But
berries were found in all the birds' guts.
A few blackbirds had
been spotted on rowan trees, beneath which berries similar to those found
inside the dead birds covered the ground. Many of these berries looked as if
they had been partially eaten.
Rowan berries are not
normally considered poisonous to wild birds, but the berries found inside the
birds smelled as if they were fermenting.
Three tissue samples
from the dead birds were sent for toxicological analysis, one of which revealed
high levels of pure alcohol (ethanol). Staff at the wildlife rescue centre to
which the live bird was sent also reported that it had been unsteady on its feet
and appeared "drunk."
The bird had had to
place its wings on the ground to steady itself, and had leant against the walls
of its enclosure to keep upright, they said. After two days the bird fully
recovered and was released back into the wild.
The authors can't
explain why only one of the samples revealed the presence of ethanol, but
suspect that all the dead birds had become intoxicated on fermented berries,
and that some of the injuries they had sustained were the result of mid-air
collisions.
