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As spring approaches in the Northern Hemisphere, we anticipate the fluttering butterflies and the capering baby lambs, and we can also expect to see some birds hammered out of their minds in the trees, and perhaps on the ground. In most cases, these birds have overindulged in the fermented berries and other fruits that froze during the winter and are now thawing - proving an irresistible treat for many kinds of birds.

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(00:00) Ah, Spring! The butterflies are fluttering and the baby lambs are capering in the fields, and the birds! The birds are hammered out of their minds on the trees.

(00:10) Have you ever seen a bird acting super weird this time of year? Like, flailing around on the ground, or flying crooked, or maybe singing sea shanties with its wing around its buddy? (00:19) Well there might be a case of too many fermented berries, it also might be that the bird is hurt or has a disease, but that's way less interesting than drunk birds. Drunk birds!

(00:28) [Intro Music]

(00:32) Late winter and early spring is when freshly thawed fruits ferment in the wild. Juniper berries, Crabapples, Holly berries, and Rowan or ash berries being among the most common. These fruits are jam packed with sugars. Jam packed. Jam!

(00:46) And all kinds of organisms love sugars because they're a great source of energy, especially after a long and hungry winter. But not all organisms metabolize sugars the same way, unlike you and me in birds, for instance, yeasts eats sugars without using oxygen, in a process known as fermentation. 
(1:04) While these tiny fungi are respiring away, breaking down the sugar for energy, they release ethanol as a by-product, and you know what ethanol is, it's the same thing that's in wine or whiskey or peppermint schnapps.

(01:14) So in the wild berries can easily ferment on their own.  That powdery coating you see on grapes or blueberries sometimes contains tons of tiny yeasts just waiting to tuck into the sugary goodness.  (1:26) Once the berries fall onto the ground or otherwise break open, it’s easy for them to infest the fruits and cause mass bird drunkenness. 

(1:34) And a fermented berry binge can be fatal, especially for young birds.  Drunk birds have been known to smash into windows and have other flying accidents, get killed by predators that they would otherwise avoid, and even die of alcohol poisoning.

(1:46) In 2010, some fifty cedar waxwings were found dead in Texas after over indulging in fermented holy berries.  (1:53) In the UK in 2011 scientists documented a dozen blackbirds dying and more found just stumbling around on the ground with alcohol from tainted rowan berries in their bellies.

(2:02) And it's not just eating fermented fruit that can cause birds to fall prey to the demon drink.  Cedar waxwings for instance don't have a crop - an expandable pouch near the throat that some birds use to store food.  (2:12) They have to store berries in a portion of their esophagus where the berries sit for a long time and can sometimes ferment inside the bird's bodies. So their little birdy livers end up being unable to keep up with the sudden  massive amounts of alcohol that yeasts are producing right in their own throats.

(2:30) The phenomenon is common enough that conservation groups even offer guidelines on what to do if you find a bird that's had too much of the berry.  If you see a disorientated bird that looks like it might not make it home safely.  You know, stuck on the ground or trying to roll out onto a busy street or picking a fight with a cat. 

(2:45) If you want, you can try to pick it up very gently with a towel and place it in a well-ventilated box in a dark, quiet place.  Once the bird begins moving around again, that probably means that it's sobered up, so you can open the box and let if fly away if it can.  If it doesn't recover within a few hours, call your local wildlife rehabilitation center for further instructions.

(3:04) And also, you can feel free to lecture the bird about drinking responsibly while it's in the box.  It couldn't hurt.

(3:10) you for watching this episode of SciShow.  You can find us on Facebook or Twitter or of course down in the comments below.  And if you want to keep getting smarter with us here at SciShow, you can go to and subscribe.

(3:21) [Outro music]