Toxicity Due to Nandina domestica in Cedar Waxwings (Bombycilla cedrorum)

Posted by: Moges Woldemeskel, DVM, PhD, DACVP & Eloise L. Styer, PhD

Many cedar waxwings were found dead in a yard in Thomas County, Georgia, in April, 2009. Five of these submitted to the Tifton Veterinary Diagnostic and Investigational Laboratory, where they were examined grossly and microscopically.

On gross examination, the gastro-intestinal tract of these birds were distended by intact and partly digested berries of Nandina domestica Thunb. (Heavenly Bamboo). These berries were the only ingesta present within the digestive tract of these birds. In all the examined birds, there were gross pulmonary, mediastinal, and tracheal hemorrhages. Microscopically, several tissues and organs including the lungs, liver, kidney, proventriculus, ventriculus, uvea of the eye, heart, the meninges and the brain were diffusely congested and hemorrhagic. The congestion, hemorrhage and edema were very marked in the lungs.

The gross and microscopic findings are consistent with lesions associated with cyanide toxicity. N. domestica berries may contain large quantities of cyanogenic compounds. For most cultivars of N. domestica, cyanogenesis is the most important intoxication factor. As seen in these cedar waxwings, in birds that die from cyanide chemical toxicosis multiple tissues or organs, particularly the lungs, may be hemorrhagic and edematous, and congested with blood. Cyanide is a mitochondrial toxin that impairs cellular respiration, causing morbidity or mortality within a very short time.

During winter and spring, when the food supplies are low or out of season, cedar waxwings migrate in huge numbers from their breeding grounds in the northern U.S. and southern Canada into the more southerly regions, where they feed almost exclusively on fruits. They often eat voraciously, until they can hold no more, and may become intoxicated from eating large quantities of over-ripe fruit.

N. domestica produce vast quantities of bright red berries, which last through the winter into the spring in this region, attracting hungry birds whose food is in short supply during this time of the year. Toxicity associated with N. domestica has not been previously reported in the cedar waxwings. However, due to their voracious feeding behavior, these birds had eaten toxic doses of the readily available berries of N. domestica.