Every wet season, helpless Australians watch as wasted parrots rain down from their skies. Elsewhere, flocks of tipsy songbirds are constantly smacking into windows, towers, and moving cars. What’s behind this airborne alcoholism? Fermented berries and nectars, which can make life miserable for careless avians. Here’s a quick primer on winged boozers. 

1. Inebriated Birds Slur Their Songs.

Pro tip: Don’t drink and tweet. In an offbeat study conducted last year at Oregon Science & Health University, captive zebra finches (Taeniopygia guttata) received spiked drinking water. According to researcher Christopher R. Olson, the alcohol rendered these test subjects “a little bit quieter” than normal and “less organized in their sound production.” Everyone’s got a buddy like that.

2. Finches Are Real Lightweights.

“We’ve yet to invent the bird breathalyzer, but we can take a small blood sample,” Olson says. By doing so, his team found that the zebra finches started acting tipsy when their blood alcohol levels reached .05 to .08 percent—just below America’s legal driving limit. Also, sobering up can be a long, arduous process because birds don’t metabolize ethanol efficiently.

3. Certain Species Have Throats that Help Get Them Drunker.

With an atypically-large liver, you’d think the Bohemian waxwing (Bombycilla garrulous) would have no trouble drinking its pals under the birdfeeder. However, as Hank Green explains above, another trait makes waxwings especially bad at handling the hard stuff: Their very stretchable esophaguses often double as temporary storage units wherein fruit can ferment internally.

4. Some Drunk Birds Will Keep Upright by Leaning on Walls.

Another tactic involves using their own wings to prop themselves up when flying’s out of the question.    

5. Avians May Learn to Identify Fruits That Can Get Them Hammered.

In 2011, a dozen English blackbirds (Turdus merula) were found lying dead for no apparent reason—until autopsies revealed fermented berries in their stomachs. Curiously, the victims were all adolescents. Why? Scientists can’t be certain, but it’s been suggested that blackbirds start to distinguish between safe and hazardous berries as they grow.