Bees and hummingbirds move from flower to flower to collect sweet nectar. While they do this, they also take in a tiny bit of alcohol that forms naturally in some blossoms.
How Much Alcohol Is Inside Nectar?
Researchers at the University of California, Berkeley tested nectar from 29 plant species. They found alcohol in 26 of them. Most samples had only trace amounts, made by tiny yeast that turn sugar into ethanol. One flower even had 0.056% alcohol by weight – about one‑tenth of the strength of a regular beer.
How Much Do the Animals Drink?
Hummingbirds can drink 50‑150% of their body weight in nectar each day. For an Anna’s hummingbird, that means about 0.2 g of alcohol per kilogram of body weight daily – roughly the same as a human having one drink.
Even though they sip alcohol all day, the birds and bees do not look drunk. In earlier tests, hummingbirds liked sugar water with up to 1% alcohol but avoided it when the level got higher.
What Might Alcohol Do to Them?
Nectar also contains chemicals like nicotine and caffeine that can change animal behavior. Alcohol could act in a similar, subtle way.
“Hummingbirds burn energy very fast, so alcohol doesn’t build up in their blood,” explained graduate student Aleksey Maro. “We still don’t know if the alcohol sends any signals that make them want to keep feeding.”
Professor Robert Dudley added, “Because they process it so quickly, they probably don’t get drunk, but the alcohol might still affect how they act.”
Experiments Show They Can Tolerate Small Amounts
At a feeder near Dudley’s office, Anna’s hummingbirds visited a sugar solution with less than 1% alcohol almost as often as plain sugar water. When the alcohol rose to 2%, they cut their visits in half.
Another study found that hummingbird feathers contain a chemical called ethyl glucuronide, a waste product that shows the birds break down alcohol just like mammals do.
How Does Their Alcohol Intake Compare to Other Animals?
The scientists estimated daily alcohol intake for several nectar‑eating birds and compared it with honeybees, tree shrews, fruit‑eating chimpanzees, and humans who have one drink a day.
- Tree shrew: 1.4 g kg⁻¹ day⁻¹ (highest)
- Honeybee: 0.05 g kg⁻¹ day⁻¹ (lowest)
- Anna’s hummingbird: 0.19‑0.27 g kg⁻¹ day⁻¹ from natural nectar
- Anna’s hummingbird: up to 0.30 g kg⁻¹ day⁻¹ from fermented feeder sugar water
Why Might This Matter?
The work is part of a five‑year project funded by the National Science Foundation. The goal is to learn how hummingbirds and sunbirds adapt to high‑altitude life, sugary diets, and sometimes fermented nectar.
“Different animals may have special ways to handle daily alcohol,” said Dudley. “Studying them can teach us more about how alcohol affects biology across species.”