What to feed garden birds?

Who’s hooked?

Suggesting that they stop feeding birds will elicit a response from many gardeners similar to that which could be expected from a smoker asked never to light up again. Watching birds devouring the food they have supplied brings immense pleasure to most people. It also has the undeniably positive spin off that it may set many people off on a life-long interest in birds. And some would say that bird watching is more addictive than smoking! In our own case, it was birding that awakened our interest in South Africa’s wonderful indigenous flora, as we started to realise how important local plants are to birds.

But, in reality, are we doing the birds a favour or does feeding merely serve to gratify our own human pleasure? There are many studies from overseas regarding the consequences of feeding birds. As was the case for many years with studies into the effects of smoking, those who arrive at negative conclusions are often shot down in flames by those whose own research, sometimes with a bias of self interest, comes to a different conclusion. But despite the conflicting reports, we now all know what the effects of smoking are, even though a few die-hards still try to deny the obvious.

With households in the USA and UK together estimated to purchase about 500 000 tons of bird seed annually, Robb et al. have reviewed the relevant scientific literature in an attempt to better understand the overall influence of this enormous food subsidy. While the studies which were included varied in design, form of supplemental feeding and species involved, the review gives an indication of the potential impact.

Unintended consequences

One concern is that regular bird feeding may create a population level that cannot be sustained by the natural food supply in the area. Thus, birds are encouraged to settle where they cannot support themselves once feeding stops. Supplementary feeding often improves breeding results and causes earlier egg laying, which is of benefit to some species. However, in others, breeding too early brings negative results, because chicks are in the nest before the period when the maximum natural food becomes available. As a result, extra food supplements on offer during times less favourable for raising chicks can lead to a decrease, rather than an increase, in the survival rate of offspring.

With some surveys estimating that as many as 75% of UK households provide food for birds, this influence of humans on the ecology of birds is undeniable and it is more than likely that it is causing considerable disruption of the natural selection process. Studies in some species have shown that an unnatural abundance of food can even alter the male and female ratio of hatchlings. Research further indicates that feeding could affect returning migratory birds which have to compete with more well-fed, abnormally strong resident species. If it has not done so already, this could affect species already in decline, such as the Willow Warbler, a summer visitor to this country. Certainly, in the UK an alarming drop in the numbers of migrants has been recorded. Researchers are still gathering evidence from a variety of possible sources, but the excessive feeding cannot yet be ruled out as a contributor to the dramatic decline, which is as high as 88% in some previously common species.

Still further overseas experience has shown that certain waterfowl chicks, which have been fed by their parents from human handouts, fall victim to a wing deformity which renders them flightless. Considering the unsuitable food, such as refined white bread that is not even healthy for humans, which is often put on feeding trays, would the situation be any different with birds’ offspring in this country? Are we not perhaps responsible for the survival of weaker birds that Mother Nature will ultimately eliminate, in a cruel starving end, when their human benefactor ceases to pamper them, and they lose the battle for scarce resources against their more hardened competitors of the same species?

What about the “leftovers”

This will be a matter of speculation until ornithologists conduct more research on the subject in this country. But what cannot be disputed is that uneaten food, left behind by the birds, will attract unwanted pests that may harm the very creatures intended to be the beneficiaries. Almost certainly at the top of the list of culprits are alien rodents, especially rats. Probably the main villain is the Norway Rat or Brown Rat (Rattus norvegicus), but there is no reason to believe that the ubiquitous House Rat (R. rattus), also known as the Black Rat, is not equally detrimental to the well being of smaller wild birds and their nestlings.

Three Red-capped Robin-Chat chicks in our garden were taken, one by one, by rats at night. This was the last to go.

On more than one occasion these imported rats have robbed the nests of Speckled Mousebirds and Red-capped Robin Chats in our Durban garden. We also strongly suspect that the nest of a Spectacled Weaver, inaccessible to most land-dwelling creatures, was raided by nimble-footed rats. A half-gnawed chick, left behind as evidence, eliminates most other urban predators. At Kloof, inland from Durban, an experienced birder similarly suspects rats, previously observed at his feeding tray, of killing and half-devouring some roosting Bronze Mannikins. As rats usually carry out their evil deeds unobtrusively, under cover of darkness, we will never know which particular bird species, and exactly how many of their nests, have become victims.

Cases of rats damaging chicks of poultry farmers are well known, while a dead Laughing Dove, lying below the windowpane into which it had flown in our garden, soon became an easy meal for rats once dusk fell. Since the elimination of feral cats from Gough and Marion Islands, albatross chicks have been viciously attacked by the introduced House Mouse (Mus musculus). Probably the world’s most widespread pest mammal, it is quite likely that it is silently just as destructive in gardens all over the country.

For smallish garden birds, the only good alien rat is a dead one!

But the most damning indictment was when we witnessed, in broad day light, a brazen attack by a rat on an unsuspecting Green-backed Camaroptera. In what almost seemed like an ambush, the rat appeared, like lightning, from nowhere. Garden birds have not evolved with these fierce foreigners and so have no natural defense. Introduced predators have been shown to kill female birds when they are incubating eggs on their nests. This is one of the reasons for ornithologists finding that in many adult bird species there are more males than females, despite the sex ratio being generally equal at hatchling level.

The single garden creature most frequently labeled as destructive by birders must be the much-maligned Vervet Monkey. Like rats, monkeys are invariably attracted to bird tables and are clever enough to make regular inspections to see what’s on offer. But, unlike the rats, they do at least belong here.

Of all the horrors placed in gardens in an attempt to delight our avifauna, the plastic sunbird feeders must be the pits. Usually made in China, it is hard to imagine how anyone could find these gaudy gadgets aesthetically pleasing and tolerate them in a garden. 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.

It has also been found that large numbers of Cape Sugarbirds congregating at bird feeders suffered from scaly-leg mite infection. This disease often decreases mobility of the birds’ legs and they may even lose their toes, which adversely affects their perching and feeding ability. As only contact transmits this infection it appears very likely that bird feeders could be a major contributor 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 function as pollinators. Many indigenous plants are exclusively pollinated by birds, so this could have serious implications for the propagation of some species of our flora that are already under threat.

But, even worse than all these scenarios, you could directly cause the death of birds, as in the 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.

The temptation to feed Woolly-necked Storks with human-made food has led to fatal results.

At Mtunzini, on the KZN north coast, an ornithologist found Woolly-necked Stork chicks dying in their nest. The culprit? A well-meaning but misguided bird lover feeding the adult parents factory processed polony, which was being carried to the nestlings!

Even the ostensibly harmless act of putting out fruit, cultivated for humans, could be detrimental to some birds. For example, the digestive systems of starlings and their avian 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.

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

Amazingly, we have witnessed bird lovers spreading packets-full of birdseeds outside their chalets in Kruger Park, in full view of conservation officials who do not seem to realise that the “Do not feed animals” signs also apply to birds!

Some natural options

For many years we have encouraged gardeners to plant indigenous through our books and gardening articles. In our own garden, with not only indigenous but locally indigenous plants, we have no need to feed birds. They are there without being enticed by human bribes! To us it is just so much more rewarding to see the birds foraging naturally in the garden rather than eating at zoo-like feeding trays. As born and bred African citizens we wouldn’t dream of visiting “reserves” where lions and other animals are fed for the sake of amusing tourists, so why should we emulate that with birds in our own garden?

Unless they receive a continuous supply of unhealthy handouts, Cape Robin-Chats provide a service to humans by feeding predominantly on ants.

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 have a definite preference for the red and orange flowers rather than the horticulturally created yellow. Some birds will even devour the flower petals! Don’t leave out the seedeaters, where 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.

Nothing beats our wild figs (Ficus species) to draw in the fruit-eaters.

Need a bath?

What then about birdbaths? Water occurs naturally in the wild and, in contrast to artificial food, it is most unlikely to harm birds in any way 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 spreading of avian diseases, but also to prevent the breeding of mosquitoes.

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

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

Once we stopped artificial feeding in our garden, and supplied only suitable local plants, the numbers of doves and other very common birds decreased but they did not disappear. However, as many more species moved in, it became a matter of quality rather than quantity. This is consistent with studies which have shown that species richness is greater in less urbanized areas. We must be among the minority of gardeners in the country who believe that all wild animals, including birds, should be provided only with natural food sources in gardens. Is this not perhaps a case similar to the historical tobacco issue where, for many years, virtually all smokers refused to believe facts they did not like?

Reading

Africa Birds & Birding. Various editions.

African Birdlife. Various editions.

Africa Wildlife & Environment. Various editions.

Anon. 2008. Community Outreach Conveys Harmful Effects of Feeding Waterfowl Eugene City Council Newsletter Dec 23: 2.

Clergeau P, Savard JL, Mennechez G and Falardeau G. 1998. Bird abundance and diversity along an urban-rural gradient: a comparative study between two cities on different continents. The Condor 100(3): 413-425.

Clout MN, Elliott GP and Robertson BC. 2002. Effects of supplementary feeding on the offspring sex ratio of kakapo: a dilemma for the conservation of a polygynous parrot. Biological Conservation 107: 13-18.

Highfield R. 2008. Feeding birds may affect migratory species. Telegraph 06 Feb.

Jannson C, Ekman J and von Brömssen A. 1981. Winter mortality and food supply in tits Parus spp. Oikos 37: 313-322.

Nilsson J. 1994. Energetic bottle-necks during breeding and the reproductive cost of being too early. Journal of Animal Ecology 63: 200-208.

Petrie M, Walsh D and Hotchkis D. 2003. Encountering wildlife without feeding. Land for Wildlife Note 20 (April): 1-4.

Robb GN, McDonald RA, Chamberlain DE and Bearhop S. 2008. Food for thought: supplementary feeding as a driver of ecological change in avian populations. Frontiers in Ecology and the Environment 6(9): 476-484.

Robb GN, McDonald RA, Chamberlain DE, Reynolds SJ, Harrison TJE and Bearhop S. 2008. Winter feeding of birds increases productivity in the subsequent breeding season. Biology Letters 4: 220-223.

Schoech JS and Bowman R. 2001. Variation in the timing of breeding between suburban and wildland Florida scrub-jays: do physiologic measures reflect different environments? In: Marzluff JM, Bowan R and Donnelly R (Eds). Avian conservation and ecology in an urbanizing world. New York, NY: Kluwer Academic.

Veld & Flora. Various editions.