WHO REALLY BENEFITS FROM FEEDING GARDEN BIRDS?

Charles and Julia Botha

Charles and Julia Botha are the authors of Bring Nature Back to your Garden and Bring Butterflies Back to your Garden. Both their books have won book prizes from the University of KwaZulu-Natal. With their kind permission, we reproduce an article written and adapted by them for Environment from one by the same authors entitled Food for thought; who benefits from feeding birds? Africa Birds & Birding, 2009, 14 (3) 36-41.

The article appears in our Newsletter in three parts. Here is the second.

Of all the horrors placed in gardens in an attempt to delight our avifauna, the plastic sunbird feeders must be the pits. It is hard to imagine how anyone could find these gaudy gadgets aesthetically pleasing and tolerate them in a garden. Recent studies in the Cape suggest that sugarbirds on the urban fringe tend to be fat and unhealthy due to the oversupply of such artificial feeders.

In another study, large numbers of Cape Sugarbirds congregating at bird feeders were found to suffer from scaly-leg mite infection. This disease often decreases mobility of the birds’ legs and they may even lose their toes, adversely affecting their perching and feeding ability. As only contact transmits this infection it appears likely that bird feeders could be contributing to its spread. In addition, other avian diseases can also spread if the liquid feeders are not emptied and washed out with very hot water on a daily basis. And, of course, if nectar eaters obtain most of their food from feeders, then they will not fulfill their natural objective as pollinators. Many indigenous plants are exclusively pollinated by birds, so this could have serious implications for the natural propagation of some species of our flora that are already under threat.

But, even worse than these scenarios, you could directly cause the death of birds, as in the recently documented case of a bird lover near Hermanus in the Cape. His bright red plastic feeder was stocked with a sugar solution containing xylitol. This substance has become popular as an ingredient in human food, often as part of low-carbohydrate or diabetic diets. In this case nearly 30 Cape Sugarbirds perished, some within about half an hour of drinking the xylitol solution. It is likely that other nectar-eaters, such as sunbirds, would also suffer the same fate.

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Starlings are best left to eat what is supplied by nature, as fruit cultivated for humans may harm them.

Even the ostensibly harmless act of putting out fruit, cultivated for humans, could have a negative impact on some birds. For example, the digestive systems of starlings and their relatives lack the enzyme to digest sucrose, a sugar found in many types of fruit. Sucrose-rich fruit, such as apricots and mangoes, can cause diarrhoea in these birds with resultant excessive water loss.

There are many options for gardeners selecting indigenous plants to attract birds. Over the years we have kept meticulous records of which plants birds favour as a food source. For fruit eating birds, the wild figs, Ficus species, are hard to beat. Other excellent options are Wild Peach Kiggelaria africana, Pigeonwood Trema orientalis, Lyceum species and the various Searsia species (previously known as Rhus). When it comes to nectar eaters, there is nothing better than our wide range of Aloe species. You will get good results from the various species of Erythrina, Leonotis and Schotia. Cape Honeysuckle Tecomaria capensis is also excellent, although birds definitely prefer the red and orange flowers to the horticulturally-created yellow. For the seed eaters, species of Panicum and Setaria grass have been recorded to feed the widest variety of birds. Other grass genera to nourish a large number of different birds are Stipagrostis and Melinis.

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Birds need water to keep their plumage in good condition, but birdbaths should be kept clean to avoid transmission of diseases spread by contact.

What then about bird baths? Water occurs naturally in the wild and, in contrast to artificial food, it is most unlikely to harm birds when supplied in gardens. Of course, diseases spread by contact, such as scaly-leg mite infection, could still spread at water baths, but the bird density at such facilities is usually much lower than at feeders. It is best to clean baths thoroughly at least once a week, not only to limit the spread of avian diseases, but also to prevent mosquitoes breeding.

Humans have also eliminated many natural sources of water as tarred and concrete surfaces prevent puddles forming after rain. And birds using rainwater filled potholes in roads face the danger of passing traffic. Swampy areas have been drained, while rivers and streams have been canalised or negatively altered in many other ways, making previously available water sources inaccessible to birds. This has deprived birds not only of drinking water, but of essential water facilities needed when moulting. In addition, climate change has brought new problems, as birds must evaporate large amounts of water to offload unprecedented heat or risk becoming exposed to fatal dehydration. At moderate temperatures some, like mousebirds, can get by without access to standing water, but under severe conditions even they must drink to balance water losses.

Next month we publish the third and final part of this article when we read about the advantages and the pleasures of using natural rather than artificial means of attracting birds to our gardens.