Are the berries on Heavenly Bamboo (Nandina) toxic to birds?
I read recently that the red berries on Heavenly Bamboo are toxic to birds and therefore should not be used in landscaping. However, these plants seem to be used everywhere - especially around commercial buildings, apartment buildings and condominiums. These are situations where a professional landscaper would be more likely to have been involved in the planting than at a residence. Why would they use plants that could harm birds?
Then the other day I was talking to a woman who has a house in my neighborhood - her yard is a "certified natural habitat" and is planted all in natives. I asked her about why people plant Heavenly Bamboo and she said that the birds were smart enough not to eat the berries. So do the birds know which ones are toxic?
I planted a Nandina last spring unaware of any berry and bird conflict. They are attractive plants and colorful and evergreen. Now I'm wondering if I should take it out.
Although all parts of the Nandina produce toxins, the berries are prompting interest and concern because they are sometimes eaten by fruit-eating birds that don't have the capacity to recognize the non-native plant's chemical risks. The waxwing mortality incident in Georgia prompted study which was reported in the scientific journal Veterinary Medicine International http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3005831/
Jerry Davis, an Extension wildlife specialist in Arkansas, saw that scientific article and wrote a news brief, which I shared with colleagues and stakeholders here in Oregon, in order to raise awareness among people who otherwise wouldn't have seen the article in the Vet Med journal. I also shared both the news release and journal article with our wildlife veterinarian colleagues at Oregon Dept of Fish and Wildlife. In the past, they have not specifically looked for Nandina as a potential cause of death because there wasn't information about the potential toxic consequences for consumers. However they noted that dead birds brought into state labs and classified as "likely alcohol toxicity" (from ingestion of fermented berries, for example) cases could have included Nandina-associated deaths that simply were not identified.
As to why it is included in "wildlife-friendly" yards, etc., Nandina was imported to the Americas as an ornamental plant quite some time ago. It evolved and is native to parts of Asia. Because ancestors of our birds of the Americas did not encounter the plant (or its toxins) historically, there would have been no opportunity for the animals to adapt to the risks (toxins) by evolving recognition or avoidance behaviors. An animal that is "naive" to a new or foreign risk literally gets no chance to learn avoidance behaviors. Imported plants and animals are not subject to testing for potential ecological interactions, such as invasibility or toxicity. Therefore, the Nandina's multi-season features such as foliage and attractive berries have seemed like a natural choice for nature-minded gardeners. Mortality events such as the waxwing incident force us to take a second look at some of these choices, however. Complicating the issue is Nandina's agressiveness and success in spreading from initial plantings to the point that it is becoming widespread in many neighborhoods and potentially invading natural areas. Much remains to be learned as to how we can assess and manage the risk, now that we know. For example, we do not yet know whether berry toxicity (or birds' attraction to the berries) and/or overall plant toxicity varies according to short-term weather events such as our recent snow events. If you want to keep the plants, you might consider clipping off the berries early in their development (prior to ripening).
Finally, other items can be found on the web: Some have advice and concerns for pet owners and owners while others are targeted at managers of plant-eating herbivores that might also have opportunities to consume the leaves or berries of Nandina.