Posted by: Sheri | August 25, 2008

Vampire hummingbird expert + urban myth remix

This has to be the weirdest place to get hummingbird information ever. Thursday night the SciFi Channel ran a B-minus horror flick called The Insatiable. Nebbishy guy holds a sluttily clad female vampire captive in a steel cage in his basement. As he and the bloodsucker chat, the talk turns to…hummingbirds. Seems he was entranced by the hummingbirds in his yard and put out a feeder for them, but they all disappeared. She says (and I’m paraphrasing only slightly), “Of course they disappeared. You gave them honey water*. It ferments into alcohol. Their systems are too delicate to handle it. But they couldn’t resist it. So they drank it until they died. If you go look under that feeder, you’ll find a pile of dead hummingbirds.”

This is one of those times when I wish I was podcasting, because sputters and choking noises are so much more expressive than mere words. I’m still trying to figure out what the scriptwriters intended that little exchange to reveal about the characters, not to mention why they thought an exclusively nocturnal creature would know or care anything about exclusively diurnal birds. What’s weird is that this was my third encounter in three days with the “alcohol kills hummingbirds” rumor.

Thursday morning a participant in a tour sponsored by Birds & Blooms Magazine asked me if I was familiar with Jack Aprill, the self-styled hummingbird guru of Leaming’s Run Gardens in New Jersey. I am, mainly because I was asked to help my friends and colleagues at the Cape May Bird Observatory deal with fallout from Aprill’s strident advocacy against feeding hummingbirds.

Aprill’s condemnation of hummingbird feeders is based on the unsupported ideas that a) sugar water in feeders rapidly ferments into alcohol, which b) is a deadly poison to the birds. Before his retirement, he reportedly preached the evils of hummingbird feeders on his guided tours of the gardens, and his self-published book with the same message is still available.

As it happens, I had reacquainted myself with Jack Aprill on Wednesday morning while drafting a response to a reporter who had been told that hummingbirds get cirrhosis of the liver from drinking fermented sugar water from neglected feeders, and that the mortgage crisis was escalating the problem because feeders were being left behind at foreclosed homes.

Are we witnessing the birth of a new urban myth? This is my first encounter with this one, and it doesn’t even seem to have hit the Internet yet (oops, I guess it has now). It sounds like a creative remix of Aprill’s alcohol ideas and the persistent myth that hummingbirds get diabetes because we feed them white sugar, though I’m unclear on whether cirrhosis figures in Aprill’s version. (If you ever took one of Jack’s garden tours or own his book, please leave a comment with details.)

The diabetes myth is easy to bust. White sugar, a.k.a. sucrose, is the main sugar found in the nectar of hummingbird pollinated flowers and not a direct cause of diabetes even in humans. Too bad the alcohol issue isn’t quite so straightforward. Home brewers and wine makers understand deliberate fermentation inside and out, but there seems to be little research relevant to fermentation rates “in the wild” and none whatsoever on the effects of ethanol consumption on hummingbirds. I’d just as soon stay in the dark on that second point than imagine some biology student or Ph.D. force-feeding alcohol to hummingbirds, but documenting the rates at which hummingbird feeder solutions ferment sounds like an excellent science fair project (hint, hint).

From my own research on free-living hummingbirds, I’m highly skeptical that alcohol presents a health hazard. Most banding studies, mine included, are based around feeders, and patterns of longevity in these studies provide insights into their impact. Feeder-using banded hummingbirds are living to ripe old ages, far longer than we would have guessed possible for such a small creature, which suggests that if small amounts of ethanol are killing them, it’s doing so very…very…sloooowly.

This makes sense from an evolutionary perspective. Any sufficiently dilute solution of sugar(s) and water, including nectar, tree sap, and the juices of overripe fruits, has the potential to ferment. If a sugar solution sits around long enough in the open air, wild yeasts will colonize it, consuming the sugars and excreting ethanol (“grain alcohol,” the drinkable kind) as a waste product. Any creature that can’t tolerate small amounts of ethanol, whether over short- or long-term exposure, would be poorly adapted to a diet of fermentation-prone nectar and should have been weeded out by natural selection long before hummingbird feeders came on the scene. In fact, as is the case for the primitive beers brewed by our ancestors, the yeasts may give natural nectar a nutritional boost, and the alcohol they excrete may discourage the growth of pathogenic microbes.

So, we can safely assume that hummingbirds must be able to tolerate some alcohol, but we still have no evidence for how much alcohol it might take to kill a hummingbird outright or lead to fatal liver disease, or even whether they get drunk. (Bees do, but at least one nectar-drinking mammal holds its liquor really well.) This is one place we commonly go astray in relating to the natural world: expecting what we know (or think we know) about ourselves to apply equally to species that evolved with vastly different opportunities and challenges. That’s the origin of the myth that white sugar is bad for hummingbirds. It certainly is unhealthy for big, sluggish mammals like ourselves in the unnatural quantities we consume these days, but in any quantity it’s a perfectly natural, even essential fuel for tiny hyperactive birds. I’m not saying that alcohol is an essential nutrient for hummingbirds, but I wouldn’t be surprised to learn that they have a much higher tolerance for the stuff than we humans, who have only had regular access to large quantities of it for a few thousand years (since we learned how to brew beer and wine).

If we err on the side of caution and assume that large quantities of alcohol aren’t good for hummingbirds, the next logical question is: Do the unnatural aspects of fermenting feeders, high volume in particular, make them unnaturally dangerous? A neglected feeder that still has solution in it after a couple of weeks might have a higher level of alcohol than almost any natural source, but would it still be palatable to the birds? In Mexico, where feeders are relatively rare, I’ve seen drought-stressed hummingbirds drinking really nasty-looking sugar water from mold-encrusted feeders that may have never been properly cleaned. This debunks the wishful thinking that hummingbirds will starve rather than drink spoiled feeder solution, but this was an extreme situation. Any flowers or fresher feeders nearby should have a competitive advantage over the fermenting feeder as the yeasts use up its sugar. It’s hard to imagine a situation in which hummingbirds would be drinking fermented sugar water consistently for months or years, the kind of chronic exposure it takes for humans to develop cirrhosis. (Unless, of course, the vampire was right and they find alcohol irresistable.)

I’m an open-minded skeptic, so if anyone has any evidence to support (or debunk) the cirrhosis claim, please contact me (especially staff and volunteers at wildlife rehabilitation centers, who would be the only people in a position to document liver disease in wild hummingbirds). In the meantime, keep up the regular feeder maintenance and support organizations that work against documented, serious threats to hummingbirds and other wildlife, such as habitat destruction, climate change, pesticides, invasive species, free-roaming cats, collisions with windows, communications towers, and other man-made obstacles, and possibly even red dyes. And don’t forget the thousands of people and pets left homeless by the mortgage crisis—they’re in dire need of our concern and advocacy.

*Addendum: The vampire hummingbird expert specified honey water, and non-fictional hummingbird experts often warn against it, too, though mainly because honey has been reported to cause a fungus-like disease of the throat and tongue (candidiasis?). This is almost an urban myth itself, as as no one seems to have any hard evidence linking the two, but there are other good reasons to avoid using honey in hummingbird feeders. The vampire was correct that honey ferments rapidly when diluted to feeder strength, in part because its main sugars, glucose and fructose, are readily used by yeasts. These simple sugars predominate in the nectars of insect-pollinated flowers, while sucrose, a disaccharide, predominates in bird-pollinated flowers and is preferred by hummingbirds. Even if honey contained the “right” sugars to feed hummingbirds, it’s extremely expensive. So for happy, healthy birds, cleaner feeders, and a bigger bank balance, stick with plain white sugar.

Related posts:

Search of the Week: “why don’t hummingbirds get diabetes”

Feeder Solution Evolution Part I: The basics

Search of the Week: “can hummingbirds get fat”


Responses

  1. The best reason not to use honey: it often contains spores of Clostridium botulinum bacteria. When honey is diluted to a water content greater than 7%, the bacteria grow and produce botulism toxin. Through normal environmental exposure, humans develop some resistance to botulism, but honey should not be fed to infants…or to hummingbirds.

  2. Hey, Lanny,

    Unless there’s some evidence I’m not aware of, we’re at the same stage with honey that we were with red dyes before all the good studies came to light: stuck with Nancy N.’s mantra of unnatural, unnecessary, and potentially harmful – all perfectly good reasons to avoid it, though not as compelling as DNA damage, developmental toxicity, and aggravation of ADHD symptoms.

    I’ve also used infant botulism as a cautionary example of the dangers of honey, but on closer scrutiny the evidence at hand for its impact on hummingbirds seems far less compelling than that for “tongue fungus” (which is almost certainly candidiasis). I say “at hand” because some of the red dye papers were several years old before I stumbled onto them, so it’s possible that there’s some research out there that relates to botulism as a hazard for hummingbirds.

    In the absence of evidence, I had to ask myself: Is it justifiable to assume that normal, healthy hummingbirds are as vulnerable to botulism as human infants? Is there something about their biology that would make them more susceptible than older humans, whose digestive acids destroy the spores or intestinal flora outcompete the bacteria? I think the answer is no. In fact, I wonder if their high food intake and rapid digestive turnover rate compared to humans and other birds would help to inhibit the growth of C. botulinum by maintaining relatively aerobic conditions in the gut?

    The other possibility is that the bacteria grow in the feeder and poison the solution. Again, this may be an unlikely scenario considering that they need anaerobic conditions to flourish. Still, it would be interesting to compare the flora that grow in a honey solution vs. sugar water and look specifically for C. botulinum and other potential pathogens. (Is there a microbiologist in the house??)

    Another issue is that the spores are everywhere, not just in honey. According to the California Department of Health Services Infant Botulism Treatment and Prevention Program: “By a process of exclusion (testing over the years of hundreds of foods, beverages and other items placed in infants’ mouths with negative results), it was concluded that most infant botulism patients acquired their spores by swallowing microscopic dust particles that carry the spores.” So hummingbirds will be exposed to C. botulinum spores no matter what we put in our feeders, but it still falls to us to avoid doing anything that would increase the risk of disease associated with that exposure.

    Here’s an in-depth review of botulism from the Wildlife Center of Virginia, and I’ve just sent a reprint request for an article on captive maintenance of hummingbirds and sunbirds in hopes that it will shed some light on the “tongue fungus” issue.

    Thanks for reading LB&E and keeping me on my toes!

  3. A comment about hummingbird longevity we consuming “old” sugar water in hot climates. We live in Louisiana where it’s often well over 90 degrees in the summer. I was told by “someone” that when the sugar water ferments the hummingbirds may become more vulnerable to predators because they they dont have their “A game”. Please respond . . .let me know if I’m being overreactive.

  4. Thanks for the comment, Jackie. As I wrote in this post, we don’t know whether hummingbirds get inebriated from consuming alcohol, so in the absence of observations of hammered hummers falling off perches, crashing into windows, picking fights with cats, drunk-dialing former mates, and/or careening around with tiny lampshades on their heads, the idea that drinking fermented sugar water/natural nectar leads to increased vulnerability to predators is nothing more than another unfounded rumor hiding behind a veneer of plausibility.

  5. I’m trying to find some info on a problem I’m seeing on a couple of hummingbirds coming to my feeder. First off let me tell you that I clean the feeders every couple of days with Dawn and a drop or two of bleach, always rinsing well. The problem is the hummingbirds tongues are always sticking out even if just sitting on a branch waiting to feed. I understand there is some kind of disease that can affect the tongue but I need more info to post on a neighborhood wildlife information site. Is this a problem created by the occasional woodpecker or finch visit to the feeder? Is it fatal? The hummers are still alive after many months of noticing this. Any recommendations or information will be greatly appreciated. Thank you

    • Don’t clean it with anything except very hot water, and a drop or two of bleach rinsing very well

    • Maryann: Your description sounds like an oral infection, but considering your diligent feeder cleaning I doubt the problem originated with your feeders. If one of your neighbors misguidedly thinks that honey is more natural than sugar, they could have unwittingly exposed the birds to candidiasis. Should you happen to notice that a neighbor’s feeder contains a suspiciously yellowish or pale amber liquid, you might point them to hummingbirds.net or this recent post at LB&E.

      Though you often see stern warnings against using soap or detergent to clean hummingbird feeders, it’s really only a problem with some poorly designed models. If all parts of your feeder are easily reached for cleaning and rinsing, you can use whatever you use to clean your own dishes without fear of harming the birds (some hummingbird feeders are dishwasher safe). If your feeder is a bottle model with an enclosed base that doesn’t come apart for cleaning, detergent or soap could remain in the nooks and crannies to contaminate the fresh sugar water. In this case, you should stick with hot water and chlorine bleach (up to 10%) or vinegar (50% to 100%) and rinse with extra care.

  6. I used to use brown sugar and water, 1 to 5 parts, and when we were given 5# of an organic raw sugar– i used that. Now i use the standard 1-5 white sugar to water AND i add a dash (about a teaspoon or so) of molasses. Our hummers love it; it adds a bit of nutrition otherwise missing from plain white sugar; it gives a dash of color to the solution, and the color changes as it ages so i can easily see as it ferments.

    • Pardon my bluntness, but you’re poisoning “your” hummingbirds. I covered this issue under the “don’ts” in my post “Feeder Solution Evolution Part I: The basics”, but let me expand on those comments in reference to yours:

      There is no molasses, nor anything like molasses, in flower nectar. However, there is substantial iron in molasses. Nectarivarous and frugivorous birds have an extremely low tolerance for dietary iron. Unnaturally high levels can accumulate in their organs, causing pain, debilitation, and eventually death. Several years ago, the Arizona-Sonora Desert Museum lost almost all of the captive hummingbirds in its collection to unnaturally high iron levels in the liquid portion of their diet, so we know from tragic experience that excess iron kills hummingbirds. If you stop this practice now, the hummingbirds that have so far survived it may be able to shed the excess iron over time before it has lethal consequences.

      A secondary point, as long as I’m in scold mode: If you’re using a color change to tell you your feeder solution is fermenting, you’re not changing your feeder solution often enough. Just get on a schedule of cleaning and refilling your feeders every two to three days in warm weather and every four to six days in cold weather, whether it looks like they need it or not.

  7. [...] about the concerns of fermented nectar, check out Sheri’s post Vampire Hummingbird Expert & Myth Remix or read more information regarding the proper nectar recipe for hummingbird [...]


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