Soon after I started working on a post focused on invasive nandina (Nandina domestica), I went down a rabbit hole and ended up in a slightly different place after I learned about the direct impact two non-native berries have on Cedar Waxwings; one of the few birds with a diet almost exclusively consisting of berries and small fruit. Waxwings are a good example of multiple ways wildlife can be negatively influenced when invasive plants replace native plants.
Invasive Plant Story #1 Poisonous Nandina domestica When I saw the first flock of winter Cedar Waxwings in my native hackberry tree (Celtis occidentalis) last week my first thought was a protective wish for them to fill up on enough native hackberries so they wouldn’t eat any poisonous nandina berries from neighboring yards. Nandina is one of the main landscape bushes in many of the monoculture yards in my area and most of Atlanta. The quantity of poisonous berries the waxwings eat is what kills them because hungry Waxwings will gorge themselves on any available berries until they can’t eat anymore! A dearth of fruiting native plants for waxwings to fill up on would mean an even higher likelihood they would turn to nandina for food. On the chance that the folks who have nandina in their yard just don’t know how toxic these berries can be to wildlife, I immediately shared my waxwing sighting and sounded the alarm on Nextdoor to alert 30k people in 23 neighborhoods nearby to cut off their nandina berries! I’m ever hopeful sharing anecdotal information will impact change.
Most people who buy and plant one or more “carefree” lacy little nandina bushes don’t have a clue that the U.S. Department of Agriculture classifies Nandina domestica as a noxious, non-native, invasive weed from China and Japan. In Georgia nandina is considered a category 1 invasive species meaning it is an exotic plant that is a serious problem in natural areas because it extensively invades native plant communities and displaces native species. It’s somewhat criminal that nandina and other perniciously invasive weeds are still sold as ornamental plants at nurseries throughout America and planted in public parks.
I can personally attest to nandina’s invasiveness. When we moved to our home over 16 years ago both our side yards were densely planted with nandina bushes. When I started relandscaping with native plants I asked my husband to remove them. We learned just how weedy they were when he valiantly tried getting every single root out. They’re hard to destroy because even a tiny root section left in the ground will regenerate and sprout. It took a few years before little nandina slips stopped coming back with vigor. Remarkably, years later they still pop up now and then!
It’s maddening to see the yards all around mine covered in nandina’s bright red berries in the winter. If you see them where you live, the best article to share with neighbors, friends, or in your local social media networks about the history and danger of invasive nandina in the Southeast is this one from Terri Johnson, a retired DNR nongame program manager and executive director of The Environmental Resources Network (TERN). Terri’s informative blog called Out My Backdoor is featured on the Georgia DNR site.
Below is brief bulleted list of the main reasons to cut berries off nandina and not plant it. Feel free to share far and wide!
Nandina berries can kill waxwings because of the massive quantity of berries waxwings will eat.
Nandina berries kill birds because they contain cyanide and cause hemorrhaging in the bird’s organs.
Nandina berries are toxic to dogs, other pets and can cause discomfort if children eat them.
There are plenty of native plant alternatives to nandina with berries birds can safely eat.
When nandina escapes from home landscapes it replaces the native plants needed for the survival of native pollinators.
Nandina is not listed as a single caterpillar host plant and birds rely on caterpillars to feed their young. No caterpillars = No baby birds
Invasive Plant Story #2 Color-Changing Invasive Honeysuckle
The impact of invasive berries on cedar waxwings doesn’t end with nandina. When I looked at the photos I took of the cedar waxwings in my hackberry tree, I noticed that a few of the birds had orangish tipped tail feathers instead of the usual bright yellow. I wondered if this was a function of the lighting or a sex difference, but it turns out the reason is related to yet another invasive plant, non-native honeysuckle. The Japanese honeysuckle is so invasive in the South that it covers 45 times more acres than kudzu in Southern forests. That’s a lot of invasive berries being eaten by birds!
Cedar waxwings get their name from the red waxwing tips that are actually appendages that increase in number and size as they get older to signal their age, maturity and social status to other waxwings. All cedar waxwings also have yellow tail tips but in the early 1960s orange tail tips started appearing. Studies confirmed the red pigment from invasive honeysuckle was the cause. If waxwings eat the berries while growing tail feathers, it changes the color of the tail tip from yellow to orange. If the red waxwing markings help sort social status, the yellow tips must also serve an adaptive purpose. The placement and intensity of the color often plays a role in mating. and the addition of an orange tip would certainly add confusion to the mix.
Waxwings are not the only birds affected by the phenomenon of invasive honeysuckle berries altering a bird’s appearance. The berries have also been documented as changing flicker feathers from yellow to pink, turning yellow-breasted chat’s namesake yellow markings orange, and intensifying the red in Baltimore oriole and cardinal feathers. The redness in male birds such as the cardinal indicates vigor and helps the strongest birds attract females. If the bird’s feathers no longer signal a bird’s body condition, it could have major implications for mate selection and ultimately the species survival. The ability of invasive berries to change the geographically specific, adaptive coloration on a bird is not only a fascinating idiosyncrasy of nature, but nature giving us a literal orange and red warning signal.
Cedar waxwings give an insight into ways non-native plants can cause a pervasive disruption to the ecosystem. Not only do they replace native plants necessary for the survival of native species, but they can actively kill native wildlife or even change the adaptive appearance of wildlife! This is yet another example of why it is so imperative to plant native plants, stay far away from non-native plants, and loudly share the damage exotic ornamental plants can do to the environment every chance we get. Telling stories can be more persuasive than just sharing facts. I would suggest sharing anecdotes about hungry winter birds gorging on deadly berries or the ability of berries to change a bird’s appearance to pique the interest of the uninformed who insist non-native plants are benign and not that big a deal.
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