MSGID: 1:317/3 64951fef   
   PID: hpt/lnx 1.9.0-cur 2019-01-08   
   TID: hpt/lnx 1.9.0-cur 2019-01-08   
    Do hummingbirds drink alcohol? More often than you think    
    Flowers, backyard feeders likely provide hummingbirds with alcohol,   
   thanks to fermenting yeast    
      
     Date:   
         June 22, 2023   
     Source:   
         University of California - Berkeley   
     Summary:   
         Animals that eat fruit or sip nectar often ingest alcohol because   
         naturally occurring yeasts turning sugar into ethanol. But how   
         do animals feel about that? A new study details an experiment to   
         determine whether hummingbirds are turned off by alcohol in sugar   
         water. At 1% by volume, no. At 2% by volume, they consume much   
         less. The implication is that hummingbirds have adjusted to small   
         amounts of alcohol likely present in flowers and backyard feeders.   
      
      
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   FULL STORY   
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   You may not realize it, but that backyard hummingbird feeder filled with   
   sugar water is a natural experiment in fermentation -- yeast settle in   
   and turn some of the sugar into alcohol.   
      
   The same is true of nectar-filled flowers, which are an ideal gathering   
   place for yeast -- a type of fungus -- and for bacteria that metabolize   
   sugar and produce ethanol.   
      
   To University of California, Berkeley biologist Robert Dudley, this   
   raises a host of questions. How much alcohol do hummingbirds consume   
   in their daily quest for sustenance? Are they attracted to alcohol or   
   repelled by it? Since alcohol is a natural byproduct of the sugary fruit   
   and floral nectar that plants produce, is ethanol an inevitable part   
   of the diet of hummingbirds and many other animals?  "Hummingbirds are   
   eating 80% of their body mass a day in nectar," said Dudley, UC Berkeley   
   professor of integrative biology. "Most of it is water and the remainder   
   sugar. But even if there are very low concentrations of ethanol, that   
   volumetric consumption would yield a high dosage of ethanol, if it were   
   out there. Maybe, with feeders, we're not only farming hummingbirds,   
   we're providing a seat at the bar every time they come in."  During the   
   worst of the COVID-19 pandemic, when it became difficult to test these   
   questions in the wilds of Central America and Africa, where there are   
   nectar-feeding sunbirds, he tasked several undergraduate students with   
   experimenting on the hummers visiting the feeder outside his office   
   window to find out whether alcohol in sugar water was a turn-off or a   
   turn-on. All three of the test subjects were male Anna's hummingbirds   
   (Calypte anna), year-round residents of the Bay Area.   
      
   The results of that study, published this week in the journalRoyal Society   
   Open Science, demonstrate that hummingbirds happily sip from sugar water   
   with up to 1% alcohol by volume, finding it just as attractive as plain   
   sugar water.   
      
   They appear to be only moderate tipplers, however, because they sip only   
   half as much as normal when the sugar water contains 2% alcohol.   
      
   "They're consuming the same total amount of ethanol, they're just   
   reducing the volume of the ingested 2% solution. So that was really   
   interesting," Dudley said. "That was a kind of a threshold effect   
   and suggested to us that whatever's out there in the real world, it's   
   probably not exceeding 1.5%."  When he and his colleagues tested the   
   alcohol level in sugar water that had sat in the feeder for two weeks,   
   they found a much lower concentration: about 0.05% by volume.   
      
   "Now, 0.05% just doesn't sound like much, and it's not. But again, if   
   you're eating 80% of your body weight a day, at .05% of ethanol you're   
   getting a substantial load of ethanol relative to your body mass,"   
   he said. "So it's all consistent with the idea that there's a natural,   
   chronic exposure to physiologically significant levels of ethanol derived   
   from this nutritional source."  "They burn the alcohol and metabolize   
   it so quickly. Likewise with the sugars.   
      
   So they're probably not seeing any real effect. They're not getting   
   drunk," he added.   
      
   The research is part of a long-term project by Dudley and his UC Berkeley   
   colleagues -- herpetologist Jim McGuire and bird expert Rauri Bowie, both   
   professors of integrative biology and curators at UC Berkeley's Museum   
   of Vertebrate Zoology. They seek to understand the role that alcohol   
   plays in animal diets, particularly in the tropics, where fruits and   
   sugary nectar easily ferment, and alcohol cannot help but be consumed   
   by fruit-eating or nectar-sipping animals.   
      
   "Does alcohol have any behavioral effect? Does it stimulate feeding at   
   low levels? Does it motivate more frequent attendance of a flower if   
   they get not just sugar, but also ethanol? I don't have the answers to   
   these questions. But that's experimentally tractable," he said.   
      
   Part of this project, funded by the National Science Foundation, involves   
   testing the alcohol content of fruits in Africa and nectar in flowers in   
   the UC Botanical Garden. No systematic studies of the alcohol content of   
   fruits and nectars, or of alcohol consumption by nectar-sipping birds,   
   insects or mammals, or by fruit-eating animals -- including primates --   
   have been done.   
      
   But several isolated studies are suggestive. A 2008 study found that   
   the nectar in palm flowers consumed by pen-tailed tree shrews, which   
   are small, ratlike animals in West Malaysia, had levels of alcohol as   
   high as 3.8% by volume.   
      
   Another study, published in 2015, found a relatively high alcohol   
   concentration -- up to 3.8% -- in the nectar eaten by the slow loris,   
   a type of primate, and that both slow lorises and aye-ayes, another   
   primate, preferred nectar with higher alcohol content.   
      
   The new study shows that birds are also likely consuming alcohol produced   
   by natural fermentation.   
      
   "This is the first demonstration of ethanol consumption by birds, quote,   
   in the wild. I'll use that phrase cautiously because it's a lab experiment   
   and feeder measurement," Dudley said. "But the linkage with the natural   
   flowers is obvious. This just demonstrates that nectar-feeding birds,   
   not just nectar- feeding mammals, not just fruit-eating animals, are   
   all potentially exposed to ethanol as a natural part of their diet."   
   The next step, he said, is to measure how much ethanol is naturally   
   found in flowers and determine how frequently it's being consumed by   
   birds. He plans to extend his study to include Old World sunbirds and   
   honey eaters in Australia, both of which occupy the nectar-sipping niche   
   that hummingbirds have in America.   
      
   Dudley has been obsessed with alcohol use and misuse for years, and   
   in a 2014 book, The Drunken Monkey, Why we drink and abuse alcohol,   
   presented evidence that humans' attraction to alcohol is an evolutionary   
   adaptation to improve survival among primates. Only with the coming of   
   industrial alcohol production has our attraction turned, in many cases,   
   into alcohol abuse.   
      
   "Why do humans drink alcohol at all, as opposed to vinegar or any   
   of the other 10 million organic compounds out there? And why do most   
   humans actually metabolize it, burn it, and use it pretty effectively,   
   often in conjunction with food, but then some humans also consume to   
   excess?" he asked.   
      
   "I think, to get a better understanding of human attraction to alcohol,   
   we really have to have better animal model systems, but also a realization   
   that the natural availability of ethanol is actually substantial, not   
   just for primates that are feeding on fruit and nectar, but also for a   
   whole bunch of other birds and mammals and insects that are also feeding   
   on flowers and fruits," he said. "The comparative biology of ethanol   
   consumption may yield insight into modern day patterns of consumption and   
   abuse by humans."  In addition to McGuire and Bowie, other co-authors   
   of the paper are former undergraduates Julia Choi and Lilianne Lee,   
   graduate student Aleksey Maro and postdoctoral researcher Ammon Corl, all   
   of UC Berkeley. The work was supported by the National Science Foundation   
   (DEB-1831833) and UC Berkeley's Undergraduate Research Apprentice Program.   
      
       * RELATED_TOPICS   
             o Plants_&_Animals   
                   # Food_and_Agriculture # Beer_and_Wine # Food # Nature   
             o Earth_&_Climate   
                   # Water # Environmental_Issues #   
                   Energy_and_the_Environment # Rainforests   
       * RELATED_TERMS   
             o Common_ethanol_fuel_mixtures o Methanol o Hummingbird o   
             Alcohol_fuel o Honey o Alternative_fuel_vehicle o Carnivore   
             o Sponge   
      
   ==========================================================================   
   Story Source: Materials provided by   
   University_of_California_-_Berkeley. Original written by Robert   
   Sanders. Note: Content may be edited for style and length.   
      
      
   ==========================================================================   
   Journal Reference:   
      1. Julia Choi, Lilianne Lee, Aleksey Maro, Ammon Corl, Jimmy   
      A. McGuire,   
         Rauri C. K. Bowie, Robert Dudley. Hummingbird ingestion of low-   
         concentration ethanol within artificial nectar. Royal Society Open   
         Science, 2023; 10 (6) DOI: 10.1098/rsos.230306   
   ==========================================================================   
      
   Link to news story:   
   https://www.sciencedaily.com/releases/2023/06/230622142345.htm   
      
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