Plants That Are Toxic to Birds!
There have been few actual documented cases of plant poisonings in birds, partly because birds enjoy shredding leaves more than ingesting them so that little may be actually eaten, because they have rapid gastrointestinal transit time so that a toxic blood level is not achieved, and because parrots have the habit of removing plant outer covering, which frequently contains the highest concentration of toxins, prior to eating them.
Signs of plant toxicity in canaries include cessation of perching, anorexia (loss of appetite), fluffed feathers, increased respiration rate, outstretched wings, and death. Most canaries that died did so within minutes to hours following the ingestion of plants. Documented plants that are highly toxic for canaries include foxglove, lily of the valley, diffenbachia, avocado, yew, lupine, and oleander. There are actually several varieties of avocados commercially available (Guatemalan, Mexican, Nabal, and Fuerte) which differ in their toxic capacity with the Mexican variety possibly non-toxic but it would be wise to avoid all types of avocado as it is just not worth the risk.
Other documented plants with mild or only transient symptoms included parsley, rhododendron, black locust, wisteria, clematis, cherry, pyracintha (fire thorn), and privet. Bird species do vary in the responses to various plants, but it is wise to avoid planting any documented poisonous plants near aviaries such as oleander (toxic foliage), Castor bean (toxic seeds and branches), pencil tree, poinsettia, and rosary pea.
My thanks to the New York Bird Club who recently contacted me with a question regarding feeding birds rhubarb that led to this blog post. A review of a list of toxic plants for cage birds printed in Clinical Avian Medicine and Surgery by Harrison and Harrison, does list rhubarb along with 53 other plants that are toxic to birds. The addition reference for this blog posting is Avian Medicine: Principles and Application by Ritchie, Harrison and Harrison.