They come in with juice-stained beaks and some less fortunate ones fly into buildings.
Birds that feed on winter berries in the Northern Hemisphere are getting loaded. Drunk as a skunk so to speak. What happens is alcohol forms in the berries as they start to ferment with the first frosts and the birds go crazy for them. It's like an open bar at a frat party. It happens much more often than we think, according to scientists.
This fall there was an episode in which a bunch of Bohemian waxwings flew into Whitehorse, Yukon, and ended up in "drunk tanks" after bingeing on fermented berries of the rowan tree.
Anticipating the problem a wildlife facility in the territory was equipped with modified hamster cages on standby waiting for the surge of berry seeking migrants. There is no bird breathalyzer test but it was pretty clear the waxwings were flying under the influence, according to Meghan Larivee, a laboratory coordinator at the government agency Environment Yukon in Canada.
"They cannot coordinate their flight movements properly or at all, and they are unable to walk in a coordinated way," she said in an email to National Geographic.
There are many reports that have come from North America and Europe describing the exact same thing but no testing has been done to confirm that alcohol was a factor in the incidents with birds in those regions. The problem is there is no test for alcohol in animals and alcohol leaves their systems rather quickly, according to Paul Duff a veterinary scientist with the U.K.'s Animal and Plant Health Agency.
In 2011 Duff confirmed a case of blackbirds in Northern England who succomed to alcohol deaths by consuming fermenting rowan berries. A liver sample was what brought him to his conclusion. The blackbirds that had died were all young; it is possible that mature blackbirds have learned to avoid the berries.
In the United States it seems that spring is when the waxwings get sloshed. Last March a berry binge led to the deaths of about 50 cedar waxwings found along a road in Harris County, Texas. National Wildlife Health Center tests showed that berries collected from a nearby Ilex shrub contained 800 ppm ethanol by wet weight -- enough to produce intoxication in these birds that could have resulted in compromised behavior and subsequent fatal trauma.
The suggestion is if you find a bird that appears to have had one too many berries, put them in a box with a little water and put holes in it. Let them sober up for a couple of hours, then set them free.