One of the saddest myths about eucalyptus is that it causes the death of small birds by “beak-gumming.”
MISLEADING ILLUSTRATION
According to this myth, small birds like kinglets foraging in eucalyptus flowers accumulate gummy residues that suffocate them. It’s all because Californian birds have short beaks compared to the longer beaks of Australian birds that co-evolved with eucalyptus. It is usually illustrated by the picture here (taken from an NPS brochure).
It’s a myth.
A new article (reprinted here with permission) by Lynn Hovland in the Hills Conservation Network newsletter describes where this myth originated, and how eucalyptus-phobes seized on it, passing it into “the conventional wisdom” as one birder phrased it. And it explains why it gets its facts wrong. In summary:
- The theory (and picture) conveniently ignores a host of small-beaked Australian birds that forage in eucalyptus.
- The source of the gum is undetermined; the eucalyptus flower is not especially deep.
- Other birders have not found numerous dead birds under eucalyptus.
Read the whole article below.
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BIRDS AND BLUE GUM: LOVE OR DEATH?
Brochures distributed by various agencies in northern California state that the flowers of eucalyptus trees kill birds. According to these brochures, birds feeding on insects or on the nectar of eucalyptus flowers may have their faces covered with “gum” and die of suffocation. Luckily for the birds, according to one brochure, most of them prefer native vegetation, and avoid eucalyptus groves.
These stories are, of course, extremely upsetting to all of us who love birds.
The bird-suffocation story began with a 1996 article by Rich Stallcup, a legendary birder who writes for the Pt. Reyes Bird Observatory. In the PRBO Observer, he reported that, on one day in late December, he counted, in one eucalyptus tree: 20 Anna’s Hummingbirds, 20 Audubon Warblers, 3 Orange-crowned Warblers, 10 Ruby-crowned Kinglets, a few starlings, 2 kinds of orioles, a Palm Warbler, a Nashville Warbler, a warbling Vireo, and a summer Tanager.
That was an unusually large number of birds, even for Stallcup to see in one tree, but what most surprised him, he says, is what he found under that blue gum eucalyptus tree: a dead Ruby-crowned Kinglet, its face “matted flat from black, tar-like pitch.”
Years before, Stallcup recalled in the article, he had found “a dead hummingbird with black tar covering its bill” under eucalyptus trees. This was all Stallcup needed to come up with his theory about what had happened.
This theory is now stated as fact in restorationist literature and it is stated three times as fact in the Plan/EIR issued by the East Bay Regional Park District in August 2009.
Ruby-crowned Kinglet, San Francisco. Credit: Will Elder, NPS.gov
Stallcup theorizes that North American birds are different from birds indigenous to Australia. He speculates that North American birds such as kinglets, warblers, and hummingbirds have evolved short, straight bills while Australian birds evolved long, curved bills. Thus, he says, when American birds with short bills seek nectar or insects on eucalyptus flowers, they have to insert their whole head into the blossom, so they get gummy black tar all over their faces.
We have great respect for Stallcup’s ability to identify birds. But we have a few problems with his theory.
Australian Weebill. Credit: Stuart Harris
1. A bird-loving friend who has photographed birds in Australia points out that Australian field guides show birds with a wide variety of bill length and curvature. When he was in Australia, he saw birds with small bills just like American kinglets and warblers. “How do you suppose the Australian Weebill got its name?” our friend asked. Many of us not so familiar with Australian birds have seen parakeets and other small small-billed parrots native to Australia. Weebills and many other American and Australian birds with small bills forage on eucalyptus leaves or flowers.
To see more birds of Australia, go to this terrific website. It features photos of many small-billed birds.
Blue gum eucalyptus flowers on tree, March, 2010. Credit: John Hovland,
2. Where’s the gum? The flower of a blue gum eucalyptus tree has no gum, glue, or tarlike substance on it or in it. The gum in “gum trees” refers to the sap or resin that, in some species, comes from the trunk. Other species of gum trees, such as the sweet gum (Liquidambar) are common sidewalk trees in Berkeley and Oakland. The flowers on the blue gum eucalyptus are white or cream-colored with light yellow or light green centers. There is no black, sticky, gummy or tarry substance in or on the living flower. In fact, both the Ruby-crowned Kinglet and the Australian Weebill are leaf-gleaners. They take insects off leaf surfaces, not from flowers. If the kinglet had gum on its face, the gum did not come from a eucalyptus blossom.
3. A euc flower looks most like a chrysanthemum, with longer petals. Unlike a morning glory, the euc flower is not shaped like a tube that a bird would need to poke its bill into to get nectar or insects. A hummingbird is more likely to pick up a sticky substance from inside a cup-shaped tulip, poppy, or any of the tiny tube-flowers such as California fuchsia, Indian paintbrush, watsonia, or honeysuckle that hummingbirds love. Common sense tells us that no bird, even a tiny one, could suffocate while feeding on a euc flower or leaf.
Photo of Watsonia, Willow Walk, Berkeley, 2010. Credit: John Hovland.
4. We have all seen hummingbirds poking their beaks into tube-like flowers. If you peel back these tube-like flowers, you will sometimes find a sticky substance on your finger. You’ve probably seen birds, especially tiny hummingbirds, sipping from these flowers. How do they escape getting nectar on their faces? An article in the NY Times proves truth is stranger than the fiction of suffocated hummingbirds. The article explains that a hummingbird gets nectar from a flower by wrapping its tongue into a cylinder to create a straw about ¾ inch long extending from its bill. This means that a hummingbird’s face does not touch the surface of a flat type of flower such as the flower of a blue gum eucalyptus.
After Stallcup wrote his article in 1997, it was accepted by birders and eucaphobes all across America. In January, 2002, Ted Williams, wrote about the “dark side” of eucalyptus in his opinion column called “Incite” for Audubon Magazine.
Stallcup, he wrote, had told him he had found 300 dead birds over the years “with eucalyptus glue all over their faces.” Williams wrote that the bird artist, Keith Hansen, who illustrates Stallcup’s articles, had found “about 200 victims.”(How did one kinglet and one hummingbird in 1997 add up to 500 victims by 2002 even though few if any other people have seen even a single victim?) Williams and Hansen also describe the suffocating material as “gum.”
Williams, in that same over-the-top column, dares to contradict Stallcup, claiming that he has heard only one Ruby-crowned Kinglet in a eucalyptus grove, and has never actually seen any birds in eucalyptus trees. Yet he repeats (and exaggerates) Stallcup’s story about eucalyptus suffocating birds. The National Park Service, U.C., EBRPD, and the Audubon Society have spread Williams’ interpretation of Stallcup’s story—apparently without questioning any part of it.
Stallcup and Williams are bird-lovers and writers. They are not scientists. David Suddjian, a wildlife biologist, has read Stallcup’s theory about birds suffocating on the “black pitch” of eucalyptus flowers, but in his article, “Birds and Eucalyptus on the Central California Coast: A Love-Hate Relationship,” he casts doubt on Stallcup’s claim that the kinglet (and other birds) could have been suffocated by eucalyptus flowers. Here is an excerpt from his article:
“. . . in my experience and the experience of a number of other long-term field ornithologists, we have seen very little evidence of such mortality. It has been argued that the bird carcasses do not last long on the ground before they are scavenged. However, when observers spend hundreds of hours under these trees over many years but find hardly any evidence of such mortality, then it seems fair to question whether the incidence of mortality is as high as has been suggested. Not all bird carcasses are scavenged rapidly, and large amounts of time under the trees should produce observations of dead birds, if such mortality were a frequent event. . .more evidence is needed.”
The Suddjian article is not generally favorable to eucalyptus trees. However, Suddjian notes that more than 90 species of birds in the Monterey Bay Region use eucalyptus on a regular basis. Additionally some rare migratory birds bring the total to 120 birds seen in euc groves. These include birds that use eucalyptus trees, leaves, seeds, or flowers for breeding, nesting, foraging, and roosting. A complete list of birds that depend on eucalyptus trees is too long to include here. We encourage you to click on the link to the Suddjian article so you can look for the names of the various bird species and note how they use—and depend on—eucalyptus trees.
The following excerpt is from the section “Wildlife” in BugwoodWiki, an article on eucalyptus globulus (blue gum) by the Nature Conservancy. It is from a field report “Eucalyptus Control and Management” (1983), compiled by the Jepson Prairie Preserve Committee for The Nature Conservancy’s California Field Office:
“Over 100 species of birds use the trees either briefly or as a permanent habitat. The heavy-use birds feed on seeds by pecking the mature pods on trees or fallen pods; so they must wait for the pods to disintegrate or be crushed by cars. Among the birds that feed on seeds in the trees are: the Chestnutback Chickadee and the Oregon Junco.
“Examples of birds that feed on ground seeds are the Song Sparrow, the Fox Sparrow, the Brown Towhee, and the Mourning Dove.
“Birds that take advantage of the nectar from blossoms either by drinking the nectar or by feeding on the insects that are attracted to the nectar include Allen’s hummingbird, Bullock’s Oriole, Redwinged Blackbird, and Blackheaded Grosbeak.
“Birds that use the trees as nest sites include the Brown Creeper, which makes its nest under peeling shags of bark and feeds on trunk insects and spiders, the Robin, the Chickadee, the Downy Woodpecker, and the Red Shafted Flicker. The Downy Woodpecker and the Red Shafted Flicker peck into the trunk of dead or dying trees to form their nests. When these nests are abandoned, chickadees, Bewick Wrens, house wrens and starlings move in. Downy Woodpeckers use dead stubs to hammer out a rhythmic pattern to declare their territories.
“The Red-tailed Hawk prefers tall trees for a nesting site. It therefore favors eucalypts over trees such as oak or bay. Great Horned Owls use nests that have been abandoned by Red-tail Hawks or they nest on platforms formed between branches from fallen bark. The Brown Towhee and the Golden-crowned Sparrow are birds that use piles of debris on the ground for shelter during rains.”
Notice that this article, written for the Nature Conservancy after weeks of observing birds in eucalyptus groves, does not mention finding any suffocated birds under the trees.
When we asked Chris Davey, president of Australia’s Canberra Ornithological Group, if there could be any truth to the story that eucs suffocate birds, he replied, “It’s a wonderful thing these urban legends!”
So how did those dead birds end up under eucalyptus trees?
A friend suggests (only half-seriously) that a few birds (including the two that Stallcup says he found) got some kind of sticky goop on their faces from another source. He theorizes that when the birds realized they were dying, they returned to the eucalyptus trees, and, chose to die under them because they had loved the eucalyptus trees so much.
—Lynn Hovland
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A few further thoughts to this article:
- No analysis of the material that apparently suffocated the birds has been published. Apparently, it was just assumed to be eucalyptus resin.
- No necropsy results indicating that the birds indeed died of suffocation was published either. The “gum” on the face could have been incidental to death from other causes.
- What about the benefits the tree provides? It helps a large number of birds to survive by providing cover and a winter food source (insects and nectar). It’s been suggested that if the eucalypts were felled, the birds would migrate south. In fact, the habitat to the south is not exactly unspoiled. Cutting down eucs would reduce net habitat, and thus, bird populations.
Finally: Here are two more short-beaked birds from Australia.
Jacky Winter, Australian bird. Photo credit "Aviceda" (Creative Commons)
Australia's Rose robin, photo credit "Aviceda" (Creative Commons)
Mount Sutro Forest That Was 
Shortly after this urban legend surfaced nearly 10 years ago, I had an opportunity to ask a local scientist about it. While attending an open house at the California Academy of Sciences, I was able to talk to the head of its ornithology division at the time.
He started by saying that although he had never seen a dead bird in a eucalyptus forest, there weren’t as many birds there because the eucalypts don’t offer as much food for birds as other vegetation types. (Those who bird in the eucalyptus forest without a nativist bias don’t agree with this generalization about a lack of birds, however.) He also said he hadn’t heard the claim.
Then, the scientist said that the story didn’t seem consistent with bird anatomy. He said that birds are capable of lifting their feet to their heads and clearing whatever might be accumulating there with their toes.
Since having this conversation, I’ve learned from the Cornell Ornithology Lab’s course in bird biology that birds regularly clean their bills by wiping them on tree branches or other surfaces, while others use their toes for that purpose. In other words, birds are unlikely to passively suffocate if their nostrils become clogged with something. They are physically capable of cleaning their beaks and nostrils.
Think about it. If your nose becomes clogged, for whatever reason, wouldn’t you lift your hands to your nose to clear the obstruction?
How could Stallcup be so far off base? Did he make up the story about suffocated birds with some motive that might have a lot to do with his dislike of eucalyptus trees? He does not even apply his knowledge of birds to solving the mystery. Since the Ruby-crowned kinglet is a leaf gleaner, there is no way it was poking its head into a euc flower.
I knew that was a fake story. I’ve never seen any dead birds in our euc forest, just lots of happy ones, and singing lustily. This was made up by the same people who accuse the poor eucalyptus of wanting to eat your young and hurl fireballs on you with their arms. Quite a few whoppers out there.
Thanks for trying to combat all the nonsense.
“Eucs kill birds” is a myth, as Ms. Hovland thoroughly establishes in her well researched, evidence-filled article.
I have asked several local ornithologists, none of whom like eucalyptus trees, if they know of any evidence to support the “eucs kill birds” story. None of them has known of any such evidence.
Last week I asked an ornithologist at the Cornell Lab of Ornithology (as reputable an authority on things birdy as you can find) if eucs kill birds. His reply contained the following points:
1) The original story claims the dead bird was a Ruby-crowned Kinglet. They don’t generally feed on flowers; they are leaf gleaners and flycatchers.
2) It is unlikely there is any gum to pick up on eucalyptus flowers.
3) Just plugging his nostrils will not kill a bird; he can breathe through his mouth. I have handled many birds with nostrils so food encrusted they couldn’t breathe through them; they were just fine when released.
4) The story could easily be investigated and verified, if true, but I find nothing about it in the scientific literature.
So “eucs kill birds” remains a myth with no evidence behind it.
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As for the bird thing I am not a bird expert and I have no evidence either way for the gumming thing but… do the short beaked Australian birds stick their faces right in the flowers? Do they possibly have behaviors adapted to avoid the possible tar than the California birds? [From webmaster: The California birds don’t stick their faces in the flowers either, actually. They were talking leaf gleaners.]
Sweetgum is not related to blue gum eucalyptus at all, for that matter nor is black gum (tupelo) related to either. The ‘gum’ refers to sticky sap, but many trees have that trait and in this case, it is evolutionary convergence – the trees are very distant relatives. I know this is kind of irrelevant to the discussion but I just wanted to point it out. [Webmaster: Uh, thanks.] Poppies don’t produce any gum like substances and I have never heard of a bird pollinating one – they are bee pollinated, mostly.
It seems that insect gleaners might have MORE likelihood of possibly getting ‘gummed up’ because if the insects are predating on the gum tree, it might be releasing sap to fight them off. Again, I am not saying that it happens or doesn’t happen because I don’t have any idea- I’ve never witnessed it.
[Webmaster: Nor could we find any record of anyone who has, except those two articles which have been very broadly propagated.]
I think most of the birds in Sutro are able to deal with urban trees and Eucalyptus and such, anyway- generalists and such.
[Webmaster: The birds think so, anyway. https://sutroforest.com/2010/03/29/sutro-forest-birds/%5D
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nice article. unfortunately two errors stick out.
1. birds do not stick their face in the flowers FALSE
I’m out looking at birds every day. The way birds forage in eukes is by licking at the nectar and picking off insects that are attracted to the nectar in the CENTER OF THE EUKE FLOWER. I’ve seen hummingbirds (Anna’s/Allen’s/Rufous), woodpeckers (Flickers and Downy), warblers (Yellow-rumped/Nashville/Yellow/Orange-crowned/Black-throated Gray/Palm/Wilson’s/Hermit) orioles (Bullock’s/Hooded) tanagers (Western/Summer) and sparrows (DE Junco/White-crowned/Golden-crowned/Song) all do it.
2. there’s nothing sticky in the euke flowers again FALSE
The center of euke flowers is a shiny center of sticky nectar.
What a quibble!
1. The birds don’t “stick their faces into the flowers.” They feed at and on the flowers as Dominik describes: licking nectar and picking off insects. The blue gum eucalyptus has open flowers which don’t require the birds to stick their faces into the flowers to get at the nectar and/or insects. There are closed flowers out there that require birds to stick their faces in (and insects to enter) to get the goodies, just not the eucs.
2. Eucalyptus flowers have nectar which is like most nectar–a bit of dissolved sugar, mostly water. It is a stretch to call it sticky; it’s no more sticky than other flowers; it is flatly false to call it “gummy.”
If you read the article carefully, you will see that it was Rich Stallcup of the Pt. Reyes Observatory who claimed that there is a sticky, tar-like substance at the center of the euc flower, and, he wrote, this substance is what suffocates birds. As anyone knows who has seen euc flowers, the center of the euc flower does not contain any tar-like substance. The nectar at the center of the flower is slightly sticky, but it would be impossible for any bird to suffocate in euc nectar. These are not the errors of the writer of the article. They are the errors of Rich Stallcup and Ted Williams that the writer of the article is disputing. The claim that eucalyptus flowers suffocate birds is ridiculous. In fact, as the article points out, there are flowers of many other plants that are tube-like in shape (unlike euc flowers), and have stickier nectar than eucalyptus flowers. They don’t suffocate birds either. Let’s give birds credit for being smart, at least about where and how to find nectar with or without yummy insects.
Very interesting article with some compelling questions. I do wonder why the author of this article (or any proponents of the euc-death theory, for that matter) did not find it important to bother consulting any botanists, since the main subject of the article is a tree. They would know best, right?
A simple Wikipedia check will tell you that the “gum” of a Eucalyptus is not a big mystery, its just sap from the bark. Whether this is what gets on the birds, or if its even eucalyptus, could probably be easily determined by mist-netting some black-faced individuals and getting the mystery crud analyzed. This would not be difficult to do, and Im sure could easily result in a publication.
It sounds like here that not only does the author not believe that Eucalyptus kills many birds (not unreasonable), but that its not even a Eucalyptus product that is on these birds at all. That is what I take issue with.
I am curious that there is no serious alternative offered here to the “myth”, either in the article or by other commenters. I know of no other nonnative tree that is so popular with birds here in California (its certainly not liquid amber). I have been birding in California since 1994 and have seen countless warblers, kinglets, etc. with tons of black “gum” stuck to their heads, faces and bills. These birds, without exception, were in or in close proximity to a large number of Eucalyptus trees, and are obviously feeding on the flowers (and/or insects in them?), despite the fact that they are considered gleaners…if you actually bother to observe Californian birds in Eucalyptus trees, you will see them doing this, whether the literature considers them gleaners or not. Furthermore, the Eucalytpus with the most blossoms always have the most birds. There is certainly a relationship between a bird’s choice of Euc tree and the number of flowers it has to offer.
Perhaps the short-billed birds who forage in Eucalyptus in their native lands really do stick to gleaning, while ours do not? Just a thought.
To claim that Stallcup’s ideas are baseless is….well, baseless, even though I agree with you that it is exceptionally unlikely that he has found hundreds of dead birds over the years under eucs. That all said, is it really true that NO birds in Australia/New Zealand every get this black buildup?
And if not, could it be because the short-billed birds are avoiding certain parts of the tree?
According to the Wikipedia article on blue gum eucalyptus, the reason the tree is called blue gum is not because of sap or gum that exudes from its trunk. It says “The broad juvenile leaves are. . covered with a blue-grey, waxy bloom, which is the origin of the common name ‘blue gum.'”
If you strip the bark from blue gum eucalyptus, the trunk of this hardwood tree does not appear to exude any gum, sap or resin. Maybe it does, but I have not observed that to happen. If the trunk is sticky (which I have not observed it to be), why does the bark peel off so easily?
I do not believe that Wikipedia can be trusted on controversial subjects that can be “edited” by those who have an agenda other than informing readers. This Wikipedia article on blue gum eucalyptus has gone through many changes, with the most heinous nativist accusations against eucalyptus removed since the last time I looked at it–so that, IMO, is a good thing, but I still would not trust it. As for the claim (under “environmental weed”) that euc trees helped fuel the 1991 Oakland Hills firestorm, I have to say, as a survivor of that fire (our house did not burn, but we were right in the middle of it, along with many big eucs that did not burn), that everything in the path of that fire burned: oaks, redwoods, bays, pines, fruit trees, ornamental plants of all kinds, shrubs, tall grass, cars, and especially wooden houses.
I have never seen any dead birds under eucalyptus trees. The live ones I have seen in and on the tree, and even pecking at branches do not have any black “gum” stuck to their heads, faces and bills.
Seagullsteve shifts the debate from “do eucalypts kill birds” to “do birds accumulate something on their faces from eucalyptus flowers.” Nothing in the article or the comments addresses the second question. The point of the article is that there is no evidence that birds are killed by visiting eucalyptus flowers for whatever purpose, insects or nectar.
The question which Seagullsteve wishes to consider is therefore of no interest. If whatever the birds have on their faces isn’t doing them any harm, why must we care where it came from? If Seagullsteve will read the comments he will see that two ornithologists have been consulted about this. They both said that birds can and do clean their faces with their feet or by wiping their faces on something. In other words, if the birds are bothered by whatever is on their faces, they will surely deal with it.
To be concerned about whether or not the birds have dirty faces seems an extreme case of anthropomorphizing. If the birds don’t care, why should we as long it isn’t doing them any harm.
@Million – I don’t think you are grasping the point. The author claims that not only do eucs not kill birds, but the gunk that accumulates on their feathers is not even eucalyptus. The whole death theory/myth/whatever is based on the fact that the gunk on the birds is, in fact, a eucalyptus product. Let me point out that nobody, on either side of this debate, is questioning that these matted-looking birds exist, most likely in a Eucalytpus grove near you.
I am a wildlife biologist that specializes in birds, and am well aware that they are more often than not capable of cleaning themselves…except when it is a particularly onerous substance that they have no adaptations for. I am sure many hundreds of thousands of birds have been “bothered” by being covered in oil, and despite their efforts to “deal with it”, they usually die. I realize that’s a dramatic example, but I think it gets the point across.
I hope that Seagullsteve will be reassured by these observations from birders posted to the SFBird email list in the past two days. I repeat: there is no evidence that birds are harmed by eucalyptus.
“I have access to a database containing 56,960 records of birds brought to a local wildlife hospital between 1992 and 2010. During this period this facility also accepted ~ 2500 birds who were classified as DOA (dead on arrival).
I volunteered in that facility for seven months during 2010 where I worked with “small birds” in order to get a better idea of how birds are being injured. I was aware then of the belief that resin, gum, nectar etc. from Eucalyptus trees might harm feeding birds.
During my time there I did not encounter any birds whose passages were blocked with any natural resins that would have prevented them from eating or breathing.
This evening I compared my observations with the 19 years of data by searching on the following keywords: “Euc”,Euk”, “Bill”, “Beak”, “Tree”,”Asphy”, “Breath”, “Mouth”, “Nar”,”Gum”, “Resin”, “Nector, “Nostril”, “Starv”,”Horn”, “Stick”, “Stuck”, “Glue”.
Preliminary Database Findings
1. There is no reference to Eucalyptus or any of its byproducts.
2. There is one reference to a bill, beak or mouth being restrained: A Cedar Waxwing who was admitted on 4/97 with a “Glued Beak”. The bird was treated and released two days later. Their lexicon usually defines “glued” as restrained by a synthetic adhesive.
3. There is one vague reference to an Anna’s Hummingbird that was “Stuck in Resin”. The bird was treated and released one day later.
4. Querying on “Sticky”, “Stuck” or “Glue” yields many records and a wide variety of species being trapped by synthetic adhesives such as rodent traps and building adhesives.
Given the ubiquitous presence of Eucalyptus in this area and the birds craving for its nectar one would expect more incidents of starving birds or ones surrendered DOA. Also, if birds did not have the capacity to preen or molt away this nectar, wouldn’t every (indulging) bird ultimately display this residue?
Obviously, 56,960 records is only a microscopic sample of the number of birds harmed or killed, even in one year. It does provide a sample for comparison of the major sources of harm that come to birds. “Trees”, until they are toppled, according to this database (and these queries), do not appear to be one of them.”
And here is another from a professional birder who is well known in the Bay Area:
“I have not banded for a while, but back in the day when I was out a lot banding with SFBBO in the south bay we used to get birds with gumned up bills/nostrils. I am sure they still show up. What I recall is that other than the bill, there didn’t seem to be any other issues with the birds. I recall they were not exceedingly worn, looking unhealthy or having low weights or anything otherwise unusual about them. However, keep in mind that this is a recollection from years ago and not a proper study. The gummed upbirds were not a taxonomically random mix, but were mainly Orange-crowned and Yellow-rumped warblers, along with Ruby-crowned Kinglets. I recall that it was mainly a fall to spring phenomenon, I do not recall gummed up birds in summer. But then again, the above species are not found in the Coyote Creek Valley in summer.”
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I kept bees for ten years on the coast near Caspar and a nearby grove of blue gum trees produced nectar during the winter which kept my bees alive when nothing else was blooming.
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I, and many other birders I’ve asked, think the gum/resin/nectar is euc-caused, though I doubt it kills birds. You only see it in euc stands, but its pretty (perhaps VERY) common (and its made me a bit disappointed when a potentially interesting warbler turns back into an Orange-crowned with the realization).
[Webmaster: Thanks for stopping by to comment, and apologies for the delay in releasing the comment. (Comments are moderated owing to spam-floods and sometimes we don’t keep up with legit comments.) The face-smearing should be easy enough to demonstrate if it’s happening – perhaps with samples for analysis during bird-banding? Also it would be useful to keep a tally to see how frequent it is, what species are affected, and under what conditions. At present, there’s no real data – only anecdotes.]
If bill gumming occurred mortality really wouldn’t be the result for most birds, and neither would it be the big problem. For every bird that gums itself up completely (if this really occurs…), hundreds or thousands more are gumming themselves up only mildly. This could reduce their efficiency or success at foraging by making them spend more time cleaning, have trouble getting beaks into small holes, have trouble singing for mates, (ad infinitum) etc… It needn’t be a large effect, birds – especially migratory ones – often operate at physiological limits (hummingbirds cross gulf of mexico, godwits fly for days straight, blackpolls make thousands of mile water crossings, etc.), and a 0.1% weight difference can be a decreased (say -1%) chance of not surviving migration (or something along those lines – the numbers are made up obviously). But that gumming might be important even if we don’t see dead birds lining up under trees.
[Webmaster: It might be. And it might be offset by the nutritional/ cover benefit the tree nevertheless provides. Bird life is all about tradeoffs – display and mate and risk being predated on, or hide and miss out; migrate and take the heavy energy cost, or stay and risk the seasonal decline in food; and so on.]
Both Stallcup’s original evolutionary argument and your rebuttal are kind of silly. First of all, bill length (or even size) doesn’t matter a great deal. In fact, a small billed bird – like a kinglet – may have greater mechanical advantage in opening a gummed up bill than a long-billed one, like a honeycreeper (or other long and skinny-billed Australian bird). It’d be like using the wrong end of a lever.
[Webmaster: The author would hardly be rebutting the argument if no one was making it!]
But nevermind the biomechanics, even if there was a bird with the same bill and same cranial musculature (as important as bill morphology), there is something else both far more important and far easier to evolve than that: behavior. Birds with a long evolutionary history with eucalyptus would likely simply avoid it – or certain parts of it – therefore their beaks/musculature/etc. would likely be under selection for different functions (i.e. prey processing, etc.).
[Webmaster: Possibly. We’re not aware of any euc-avoidance behavior in Australian birds. As far as we know, they use the tree as a resource in much the same way as birds here. If you are aware of any such research or observations, we’d be interested to see it.]
While I don’t think I disagree with you, its a bit shoddy to assume that because you (and others, including me) haven’t seen dead birds, a) its not eucalyptus (it almost certainly is – you bet Rich Stallcup wouldn’t get that wrong) and b) that it doesn’t negatively effect them – that could manifest itself without killing them.
[Webmaster: We believe Stallcup would have been excellent at identifying the birds, but he did’t provide any evidence that the material on the bird was actually from eucalyptus. We’d be interested to see an analysis as we described above.
And if there is such ‘gum’ – we don’t know if it does affect them negatively, and we also don’t know if the other benefits from euc-habitat offset or more than offset such a putative negative effect.]
Setophaga concedes that there is no evidence that eucalypts kill birds, but speculates about many ways in which the birds could still be harmed by them.
One could just as easily speculate about the ways in which eucalypts could benefit the birds: the availability of nectar and pollen during the winter months in which little else is blooming, the availability of food at the beginning of the nesting season, the availability of insects that are attracted to the nectar, the availability of tall trees in an otherwise treeless landscape to provide shelter from the wind as well as places to nest and roost, etc.
The nativist viewpoint is dark and gloomy. Every non-native species in the ecosystem is presumed to be harmful. If the species in question were native you can be sure the speculation would be as positive as it is negative when the species is non-native.
I am unable to prove my speculation about the benefits of eucalypts to birds, but you can be sure that Setophaga cannot prove that they are doing any harm. The truth is often found in the middle of such disparate viewpoints. Here is an article that reports that at least two species of birds are definitely benefiting from eucalyptus trees in California: http://milliontrees.me/2014/07/26/birds-and-butterflies-in-the-eucalyptus-forest/
Here is another analysis of the evidence that eucalyptus is not harmful to birds: http://milliontrees.me/2013/11/05/eucalyptus-trees-do-not-kill-birds/
You clearly don’t get my point. I agree – we need evidence (and I suspect eucs are just fine for birds – I seek out stands during warbler migration!) – but its just as bad that unproven assertions are used in this article as in the other (e.g. your final sentence “not harmful” is actually not what the article is addressing – they don’t kill birds, but that doesn’t mean they are “not harmful”). This is not an innocent until proven guilty situation – this should be an entirely neutral until proven one way or the other – the burden of proof is on both sides.
You don’t have any evidence that eucalyptus are good for birds, either, besides that we see them in them (I agree with you – I think they are). Yes, Anna’s hummingbirds feed on them and nest in them; but that’s not evidence they are good for the birds (they could be an ecological trap, a preferred, or simply utilized, habitat or resource that actually reduces fitness of the species: this is REALLY common with invasive species – I don’t think its actually occurring, but to dismiss it out of hand is unwise [and deceitful – you and others clearly have agendas in this issue]). To do that study, we’d need to compare areas without eucs to those with. I think this would be context dependent, the effect of eucs might differ (positive or negative) on the northern coast, the southern coast and the valley, given characteristics of food availability, etc. with other trees.
And we do have evidence that the gunk is eucalyptus-based – we only see gunked birds in eucalyptus groves (this isn’t a solitary observation – Stallcup noted it, Steve noted it above, I’ve seen it in California AND several places in South America and the few birders [2] I’ve asked since I saw this post all have seen it – all in euc groves). Yes, that is the definition of circumstantial evidence (in the circumstance of being in eucs, we often see gumming), but the sample size is high, 6 people and likely hundreds of birds. I’ve only seen it on warblers and kinglets in California (and similar insectivorous birds abroad) – an observation that seems standard less Stallcup’s hummingbird – which is an interesting twist, but not one that makes it more or less likely to be euc. If it is euc-caused, does that mean its harmful… probably not, but who knows? Let’s not reject that out of hand, either.
I think someone should interest the PRBO folks in keeping records of this (your argument that the hostpital database contained no entries is not convincing; who knows whether it would be noted and again, the morbidity vs. mortality is at work – this resin doesn’t kill birds directly, no one is disputing that – but if it gums up nostrils and reduces metabolic efficiency, it might be more susceptible to a cat or hawk – and the reason listed on a vet form would be lacerations, etc., not resin).
It would obviously be also useful to get samples of it (just because nectar feels watery – it does – doesn’t mean that over time it doesn’t get gummy – epoxy is a liquid at first, too).
You guys (webmaster/milliontrees) sort-of accuse me of having an agenda – I do: getting to the root of this using evidence-based science – and rejecting bad arguments, on both sides. I have no particular dislike, or attachment to, eucs, but this is an issue that we – as birdwatchers and conservations – should try to think about rationally, without letting any ideas we have about native/nonnative come into play. There are good examples of both sides; Eastern Goldfinches eat almost exclusively nonnative thistle seeds and time their nesting to when thistle seeds are out. Alternately, tamarisk ruins hydrology and vegetation structure for a number of riparian birds in the southwest. Some characteristics of euc will certainly come down on both sides (for instance, here in the valley, acorn woodpeckers would certainly gain a huge amount of habitat if riparian euc stands were replaced with valley oak – but other birds might suffer!).
No one here is arguing against a rigorous scientific study which would definitively address the question of whether or not birds are harmed by eucalyptus. Until such a study is done, your speculation about harm is just that….speculation. As long as such negative speculation continues, you will continue to find responses from those who are unprepared to destroy hundreds of thousands of trees based on such speculation.
And so, I will take up several of the negative statements you make in your latest round of speculation:
• You say: “Yes, Anna’s hummingbirds feed on them and nest in them; but that’s not evidence they are good for the birds (they could be an ecological trap, a preferred, or simply utilized, habitat or resource that actually reduces fitness of the species.” Had you read the link I provided about Anna’s hummingbirds and Red-Should Hawks using eucalyptus, you would know that the Cornell Ornithology Lab (the country’s most prestigious ornithology research institution) reports that the population of Anna’s Hummingbirds has significantly expanded its size and range in California because of exotic trees, specifically mentioning eucalyptus. The best measure of “fitness” is reproductive success. Therefore, it is not accurate to claim that eucalyptus could be an “ecological trap” for Anna’s Hummingbird.
• Secondly, the “ecological trap” accusation about non-native plants is a common argument used by nativists and one that is contradicted by the reality of huge increases in bird populations associated with the presence of non-native plants. Here is an article debunking a similar claim made about cardinals and honeysuckle in Eastern and Mid-Western states: http://milliontrees.me/2014/03/25/are-non-native-plants-ecological-traps-for-birds-part-ii/.
• You say, “Alternately, tamarisk ruins hydrology and vegetation structure for a number of riparian birds in the southwest.” There are studies that contradict this statement on two counts. First, the decline in water sources has in many cases preceded the establishment of tamarisk. In those cases, eradicating tamarisk does not restore water that was previously diverted for other purposes. Therefore, eradicating tamarisk does not restore the native vegetation which requires more water than tamarisk. Secondly, and more importantly, tamarisk is providing valuable habitat for birds, particularly the endangered Southwestern Willow Flycatcher. Tamarisk eradication efforts have been stopped in some places where the population of this endangered bird is now dependent upon it. http://milliontrees.me/2010/12/15/invasion-biology-confusion-about-cause-and-effect/
The original publication of Stallcup’s theory that eucalyptus is harmful to birds is nearly 20 years old. If there were any empirical evidence to support this claim there has certainly been ample time to find it and publish it. Meanwhile, in the absence of such a study, you are free to speculate about harm and you can expect that your speculation will be questioned. There is nothing “deceitful” about our questioning your speculation. We have not fabricated any “evidence” or said anything that is more speculative than statements you have made.
There’s nothing “silly” about debunking Stallcup’s story that eucalyptus kills birds by beak gumming. The Stallcup story, spread by Ted Williams in Audubon magazine, is believed and repeated by many people in the Bay Area. People believe the false story, and seriously use the story to argue for certain public policies. The story has appeared in publications of the National Park Service and the California Invasive Plant Council, and is used to justify eucalyptus destruction on public land. It is a public service to debunk the evidence-free story.
It may be progress that here the claim of fatality to birds is toned down to a claim of some other possible harm to the birds. (I wonder how many Audubon members would accept the changed story.) But there is still no evidence—no evidence of any harm at all, much less significant harm. No one has assumed that it’s not eucalyptus or that it’s not harmful. To say there is no evidence is not to assume anything. But it appears that Setophaga has assumed that it is eucalyptus and it is harmful; the burden of evidence is on him.
Beak gumming and dark smudges on birds’ faces are two different phenomena. Photos published on the SFBird list-serve, allegedly showing beak gumming, actually just showed smudges on the facial feathers around the beak. Further, the smudges didn’t mat the feathers around the beak, and showed no sign of being sticky.
Discolored feathers on birds occur in the absence of eucalyptus. I have seen orioles in tropical cities so discolored by sooty-appearing feathers that they were very hard to sort out by species. The discoloration may or may not have had anything to do with trees. But the trees in the area were palms, ficus, cecropia, ceiba, as well as many ornamentals.
http://seagullsteve.blogspot.com/2015/01/the-rustic-bunting-bicolored-blackbirds.html
Worth a look, though it doesn’t prove anything, it illustrates the phenomenon nicely.
The usual explanation for birds breathing through their mouths is that they are hot and this is the most efficient way for them to cool off because they do not have sweat glands. Seagullsteve’s interpretation of the bird’s behavior is an extreme case of anthropomorphism. He sounds more like a psychoanalyst than a birder.