Eradicating non-native plants is taking the food out of the mouths of birds

Plants have many different strategies to ensure their reproductive success.  Sometimes they are passive participants in their propagation.  Charles Darwin studied the dispersal of the seeds of plants and reported a particularly stunning example:  “He raised more than eighty plants from the mud-ball gathered round a wounded French partridge’s leg.”*  He also raised plants from seeds found in the stomachs of birds, which brings us to today’s topic:  the non-native plants which are eaten by birds are categorized as “invasive” plants and are therefore doomed to be eradicated.

We often puzzle over the list of nearly 200 non-native plants on the list compiled by the California Invasive Plant Council (Update:  Now nearly 300 in 2020).  We know from horticultural experience and scientific studies that at least two of the trees on this list are not invasive.  Aerial photographs of open space in the Bay Area taken over a period of 60 to 80 years, proves that neither the eucalyptus nor the Monterey pine forests are spreading. 

Cotoneaster lacteus. Jackson Nursery, UK

There are also several species of non-native shrubs which produce berries on the list of “invasive” plants that we know don’t spread in our gardens:  English holly trees, Cotoneaster, and Pyracantha.  So, why are they on the hit list?  The garden columnist in the San Francisco Chronicle recently told us why in answer to a question about planting a non-native holly tree for Christmas foliage in the garden:

Berries are a little harder to come by if we follow the advice of native plant specialists who are concerned about escape of holly, cotoneaster and pyracantha into nearby wildlands, particularly in coastal counties. Birds that eat the fruit and deposit seeds are the culprits.” 

Pyracantha. Wikimedia Commons

In other words, native plant advocates don’t want gardeners to plant non-native plants that produce berries that birds eat because they don’t want the plants to spread.  Obviously, their dedication to native plants trumps whatever concern or interest they might have in the welfare of birds.  Native plant advocates frequently claim that their “restorations” will benefit wildlife.  Clearly the eradication of berry-producing shrubs does not qualify for such a claim.

The loss of food and habitat for the wildlife that lives in our public lands is only one of many issues in the debate about native plant “restorations.”  But for bird lovers, this is a high priority.  In this regard, we were struck by one of the public comments that was recently submitted on the Draft Environmental Impact Report for the Natural Areas Program.  This self-identified “birder” said this about the radical “restorations” in San Francisco:

“Restoration areas such as Land’s End, El Polin Spring, Crissy Field are seldom spoken about anymore by birders or others looking for populations of wildlife.  Since the vast majority of the city’s resident bird species feed, roost and breed in trees, they leave, starve or are predated when their habitat is destroyed.”

Cedar Waxwings in crab apple tree. Wikimedia Commons

As the Cedar Waxwings pass through the Bay Area on their annual migration, we see them eating the berries in our holly tree.  They remind us that the eradication of non-native trees benefits neither animals nor birds, nor insects.  Who benefits from these destructive projects besides the people making their living at it?  It’s a mystery.

* Mabey, Richard, Weeds:  In Defense of Nature’s Most Unloved Plants, HarperCollins, 2010, page 29

Another Eucalyptus Myth: Bird Death According to Audubon

As we have said in other posts on Million Trees, those who demand the destruction of non-native trees justify their demand by making many critical claims about them.  One of the most disturbing of these claims is that eucalypts kill birds.  Reprinted here with permission is an excerpt from an article in the April 2010 newsletter of the Hills Conservation Network which debunks this myth.

The Hills Conservation Network is a group of residents in the Oakland-Berkeley Hills who advocate for fire safety without clear-cutting non-native trees.  Most of the members of the network are survivors of the 1991 fire in their neighborhood.  Some lost their homes.  Some lost members of their family.  They are highly motivated to improve fire safety in their neighborhood and they strongly believe that fire hazard mitigation can be achieved without destroying all non-native trees. 

Please visit their website  to see other issues of their newsletter which is a valuable source of information on the subject of fire hazard mitigation.  You may subscribe to their free on-line newsletter by sending an email to



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 “Wildfire Plan”/EIR issued by the East Bay Regional Park District in August 2009.

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.

Misleading illustration from Stallcup article

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.


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 1996, 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 1996 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.

Lynn Hovland


Million Trees Webmaster:  Shortly after this urban legend surfaced over 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 in San Francisco, 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.   

Ten years and many walks in the eucalyptus forest later, we have yet to see a dead bird, but the myth lives on.