A rumor has been circulating among birders in our area (Puget Sound) regarding the toxicity of nandina berries to birds, specifically cedar waxwings. I use a fair amount of nandina in my landscape designs, so this is obviously a concern.
How toxic are nandina berries for wildlife? How often do birds or other critters eat enough of the fruit to be damaging?
I think that people are probably referring to this study:
Excerpt:
“Nandina domestica berries contain cyanide and other alkaloids. For most cultivars of N. domestica, cyanogenesis is the most important intoxication factor. Cyanide glycosides are substances present in many plants that can produce highly toxic hydrogen cyanide (HCN). At least 2000 plant species are known to contain cyanide glycosides with the potential to produce HCN poisoning. Generally, most parts of the plants contain cyanogenic glycocides [sic], the young rapidly growing portion of the plant and the seeds containing the highest concentration. At least 55 cyanogenic glycosides are known to occur in plants, many being synthesized from aminoacids as part of normal plant metabolism. Frost and drought conditions may increase cyanogenesis in some plant species. Cool moist growing conditions enhance the conversion of nitrate to aminoacids and cyanogenic glycosides instead of plant protein. Presumably, similar weather conditions during late winter and early spring in the study area might have favored increased cyanogenesis in N. domestica.”
Note that this is the first time a mass death of waxwings has been observed, studied, and related to Nandina. Also note that Nandina is invasive in southern states (which means there is probably a lot of it in Georgia, where the deaths were noticed). If there are diverse food sources for the birds in the landscapes you design, perhaps consumption of a few Nandina berries is less of an issue. Another thing to note is that there are a great many other plants whose fruit contains cyanogenic glycosides, and we are unlikely to be able to avoid planting every single genus with this characteristic.
You could aim to plant several plants in each landscape you create which are the preferred diet of local birds. Here is information about the cedar waxwing’s feeding habits.
Excerpt:
“Cedar Waxwings feed mainly on fruits year-round. In summer, they feed on fruits such as serviceberry, strawberry, mulberry, dogwood, and raspberries. The birds name derives from their appetite for cedar berries in winter; they also eat mistletoe, madrone, juniper, mountain ash, honeysuckle, crabapple, hawthorn, and Russian olive fruits. In summer Cedar Waxwings supplement their fruit diet with protein-rich insects including mayflies, dragonflies, and stoneflies, often caught on the wing. They also pick items such as scale insects, spruce budworm, and leaf beetles directly from vegetation.”
The rumor continues to arise from time to time, because of social media. This article by Mike Darcy, from the April 2014 issue of Digger, is helpful. In it, he quotes Nikkie West, the backyard habitat coordinator for Audubon in Portland, Oregon:
“We have not taken in any birds at the Wildlife Care Center that have displayed the symptoms associated with the Nandina berry, nor have our wildlife veterinarians heard about the issue within rehabilitation circles and professional affiliations in the Pacific Northwest. […] Of the approximately 3,000 birds we take in at the Audubon Wildlife Care Center each year, domestic house cats are by far the largest cause of injuries — about 40 percent. Due to the types of injuries sustained, these birds
have a low survival rate.”