It’s only mid-September, but already some of our favourite rhodos are blooming: ‘Cornubia,’ ‘September Snow,’ and R. Delavayi are just three in a long list of colourful winter delights. Yet what’s not so delightful about these, and other rhododendron, at least for our feathered friends, is the toxicity associated with the plants. Many of us who have never heard of the danger rhododendrons pose to birds, are aware of what these shrubby garden ornamentals can do to livestock, should they ingest them – especially when the foliage has been left in a pile to dry off, and become more attractive to the likes of sheep and goats. The rhodo toxin that can kill livestock is called ‘grayanotoxin’ and it is found in varying levels of concentration, depending on the species of the rhododendron. Those rhodos exhibiting the highest levels of grayanotoxin originate from Nepal and regions of Turkey close to the Black Sea, where their poisonous ‘attribute’ has helped protect them from browsing animals.
It’s not only in the foliage of rhododendrons where grayanotoxin is found. In fact, the toxin is contained in all parts of the plant, including stems, flowers, pollen, and nectar. While you may well be nodding as you realise why these plants pose a problem for nectar feeding birds, there are several other ways, other than through nectar, birds can ingest grayanotoxin. When insectivorous birds feed on insects that have consumed parts of the rhodo, the birds become infected with the toxin. Birds nibble, out of curiosity, on the rhodo’s blooms, or can accidentally ingest small, dropped, parts of the plant while ground feeding, and can succumb to the poison.
When birds do ingest grayanotoxin, the results can be lethal as the poison leads to both gastrointestinal and heart-related issues. Many gardeners are reluctant to believe the severity of the complications birds can suffer, in part because they have never spotted birds in their garden exhibiting symptoms. However, although the toxin can have an almost immediate effect on birds, it can also take several hours before symptoms set in – by which time the affected birds are likely to have left the property where the rhodos are grown.
Anyone who has spotted a bird poisoned by grayanotoxin will have no doubt about the severity of the symptoms. Tremors, seizures, convulsions, regurgitation, uncoordinated movements, lethargy, and weakness are all symptoms of poisoning. Birds may also exhibit raucous, distressing cries of pain. If help is not at hand, in the form of a nearby wildlife clinic, some of our most beloved garden birds, including tui and bellbird, will die.
As gardeners, and bird lovers, we face a dilemma. However, it’s not insurmountable, because there are steps we can take to help our feathered friends, while also enjoying colourful displays of flowers. Obviously, if you are prepared to remove the rhododendrons you have, this is the best solution to the problem, and one to be encouraged. If you are prepared to do this, there are many other, beautiful flowering shrubs and trees you can use to replace your rhodos (check here for suggestions). If removing your rhodos is not something you can entertain, consider providing alternative sources of food such as a nectar dispensed from a feeder positioned well away from your rhododendrons. This may satisfy your nectar feeding birds in early winter, when there are few flowering plants about. Always be mindful of what is going on in your garden, and if you spot nectar feeding birds showing an interest in your rhododendron flowers, net the shrubs until other non-toxic flowering plants are available. If you do spot ailing birds, be sure to notify your nearest wildlife centre immediately.
When birds in our gardens bring us so much joy, the least we can do by way of thanks, is to care for them through responsible planting and garden management.