February 21, 2024

If your local hummingbird becomes a bit aggressive, it may have a drinking problem. In addition to nectar, hummingbirds also get alcohol from flowers and feeders, according to a recent study by UC Berkeley biologist Robert Dudley.

To boost their metabolism, hummingbirds consume up to 80 percent of their body weight daily on a diet of nectar or sugar water, supplemented by protein from catching small insects or stealing them from spider webs. Hummingbirds are jerks to spiders.

In the wild, however, yeast and bacteria are ubiquitous and can ferment these sugars into alcohol. The concentration is very low, but when you drink as much as a hummingbird, you get more than just a sugar high.

To study this, Dudley had his team of undergraduates feed three male Anna hummingbirds spiked sugar water of varying alcohol concentrations (anna caliput) live outside the lab and see how they react.

They found that when the concentration was as high as 1%, the hummingbirds swallowed the sugar like regular sugar water. If the concentration is increased to 2%, the poultry drink half as much water, so they get the same amount of alcohol in half the total liquid volume.

According to Dudley, this suggests that in the wild, the alcohol concentration may not exceed 1.5 percent.

When the feeder sat, the concentration dropped to 0.05% as the alcohol evaporated, but that was still a lot of alcohol for such a small animal, and drank as much as a hummingbird. However, the hummingbird’s metabolism continues to go into overdrive, so the alcohol is burned off before it can be crushed and a bar fight started.

“This is the first time that birds have been shown to consume ethanol in the wild,” Dudley said. “I would use the phrase with caution because this is a laboratory experiment and a husbandry measurement. But the connection to natural flowers is clear. It just goes to show Nectar-eating birds, not just nectar-eating mammals, not just fruit-eating animals, may all be exposed to ethanol as a natural part of their diet.”

The next step in the research will be to investigate what role alcohol plays in the diets of Old World sunbirds and Australian honeyeaters.

The study was published in Royal Society Open Science.

source: UC Berkeley