Why do we feed our garden birds?

New research has shown that feeding birds might not be quite the benefit for wildlife we think it is. Two of the paper’s authors, Jack Shutt and Alexander Lees, explain why this might be the case.

Globally, humans have fed wild birds for a long time, and this feeding takes many forms. Some is clearly evidence based and conservation motivated, like providing seeds for declining farmland birds to see them through the ‘hungry gap’ or putting out carrion at ‘vulture restaurants’. Both are emergency solutions aimed at halting declines. Other feeding is clearly to benefit us humans, like providing fish for Whitetailed Eagles or worms for antpittas to attract tourists.

The most common form, however, is feeding the birds in our gardens.

This is big business, valued at US$6 billion globally. Widespread garden bird feeding is actually a relatively recent phenomenon, starting in the 1970s and really taking off in the last 20 years. Nowadays, around half of all UK households spend £280 million annually, dispensing almost 200,000 tonnes of bird food.

This amount of food is enough to feed more than three times the entire populations of feeder-using birds if they ate nothing else and is distributed through an average of 100 feeders per square kilometre – more than one for every nine individual birds that might use it. Intuitively, this seems like a good thing: more food for the birds, many people inspired by nature and lots of bird-based enjoyment to be had by all. This is the win-win story that we are used to hearing in the UK – that ‘our birds need us’. But is this true?

On the up

Certainly, species that use garden bird feeders are generally increasing in numbers, and it has been shown to improve their survival rates and breeding densities quite dramatically.

It is also clear birds will travel long distances to access this resource, with Blue Tits shown to travel several kilometres daily to visit feeders, and more mobile species even further. Combined with the density of feeders in the UK, this means it is likely that the vast majority of individuals of feederusing species now have access to an almost unlimited, energy-rich, easyaccess food source.

Such an enormous input of unnatural resources into the environment must have equally large, ecosystem-level impacts. The most obvious are changes in populations, with feeding helping Great Tits increase by 40% and Great Spotted Woodpeckers by 143% in the last 25 years, for example. However, feeding has also led directly to declines. By encouraging unnatural long-term gatherings of several individuals of many different species in a single space, we provide ideal conditions for diseases to transfer between birds and even species.

Greenfinch has been Red listed in the UK following a two-thirds decline due entirely to the disease Trichomonosis caught at garden bird feeders. This disease has recently spread to Redlisted Hawfinches, where they are fed sunflower seeds alongside Greenfinch, and has also been implicated in recent declines of Chaffinch, Collared

Dove, European Turtle Dove and potentially even Eurasian Sparrowhawk. Papillomavirus (‘bumblefoot’), E coli infections and tit pox are also spread primarily around feeders.

While cleaning and moving feeders does reduce the risks, let’s be honest with ourselves – how many of these millions of feeders are cleaned even monthly?

Is it responsible to continue to advise unlimited feeding and then add “clean your feeders” as a throwaway line?

There are also indirect risks to threatened species from bird feeding. Encouraging them to visit gardens increases deaths caused by household pets and window collisions. Boosting populations of feeder-using species may also increase the populations of their natural predators, which may then take more individuals of non-feeder-using species than they have previously (an effect known as hyperpredation). And

a lot of bird food is eaten by animals that it wasn’t intended for, including squirrels, rats, foxes and corvids, which are important nest predators of several threatened species.

Outcompeted

Many of the species that compete with feeder-using species, but use feeders less or not at all themselves, are declining, and being outcompeted by unnaturally large populations of feeder-using species may be part of the problem. Marsh and Willow Tits are Red-listed UK woodland species that have suffered catastrophic declines in recent decades. The reasons for these decreases are largely unexplained, with changes to their habitats and the climate both invoked as possibilities, but studies have failed to prove any connection.

Marsh and Willow Tits are naturally subordinate to Great and Blue Tits, but have evolved strategies in order to compensate. They occupy large, yearround, lifelong territories which they know inside-out. This enables them to find natural foods quicker and exploit them before being displaced by the dominant tits, and also cache food and remember where it is, giving them an advantage in hard winters. But if there is no longer a bad winter due to garden bird feeding, can increased numbers of competitors empty the woods of food and then simply move on to garden feeders, leaving the Marsh and Willow Tits stranded?

Things might be even worse for Willow Tits, which excavate their own nesting chambers, allowing them to occupy scrubby woodland to avoid competition. This tactic works well in natural conditions, but we know that the two leading causes of Willow Tit nest failure are being evicted from their laboriously excavated nests by Blue Tits and being predated by Great Spotted

Woodpeckers, both species now more abundant due to bird feeding. For a full investigation of these possible impacts, we recommend reading our recent article in British Birds (Broughton, Shutt and Lees 2022). Could bird feeding partly explain these declines, and also factor into the unexplained declines of other woodland species such as Lesser Spotted Woodpecker, Pied Flycatcher and even Wood Warbler?

This idea isn’t new and is one reason why garden bird feeding has been discouraged in Australia for decades. There, where birds are routinely fed, several super-dominant species (including Noisy Miner and Rainbow Lorikeet) monopolise the food, allowing them to aggressively exclude all other species from the area, drastically reducing bird diversity. In New Zealand feeding helps invasive species push out natives.

While these impacts may be more obvious there, this doesn’t mean that they’re not occurring here more subtly, possibly allowing dominant species to take over communities and helping nonnatives such as Ring-necked Parakeet invade. Given the ubiquity of feeding in the UK these competition impacts could eventually reduce local bird diversity in many areas to just those common species that take advantage of it, while eliminating more specialised species which don’t, contributing to a loss of species diversity in UK woodlands.

Eco impact

Quite aside from the costs and benefits to our own garden birds, we should

also consider the environmental impact of bird feeding. Looking at average yields for sunflowers and peanuts, a quick calculation reveals that 7001,000 square kilometres of land are required annually to provide bird food just to British gardens. To put this into context, that is roughly the same area as all the UK’s National Nature Reserves combined, or the same area as Dartmoor National Park. Imagine if, instead of being under non-essential intensive agriculture to provide garden bird food, this area was left as natural ecosystems – wouldn’t the wildlife benefit be far greater? To compound this, much of the land used to cultivate garden bird food is in more biodiverse regions with greater wildlife costs from agriculture, with peanuts from tropical East Asia, sunflowers from eastern Europe, and nyjer from Africa and India. Then add in the fertiliser, pesticide, water and machinery costs of production, all the plastic packaging and the fuel costs of transporting the seeds halfway around the world and you start to wonder about the enormity of the environmental footprint.

However, before we get too disheartening about the negatives of bird feeding, we do want to point out one thing: it is undeniably good for us

❝UK households spend £280 million annually dispensing almost 200,000 tonnes of bird food❞

humans. Feeding garden birds improves our mental wellbeing, gives a lot of happiness and provides a vital link to nature in a world that is otherwise drifting away from it. Interacting with birds at feeders is what starts many people’s interest in nature and can lead to many positive environmental behaviours, and this is certainly something that should be encouraged.

This does raise a slightly uncomfortable question, though: why are we really feeding our garden birds? Is it for the birds’ benefit or our own enjoyment? If it is for the birds, which species do we think will disappear without us feeding them? Some populations of very common species might fall back to natural levels, but that isn’t a bad thing. Despite the advertisements, how many of us are actually supporting Common Linnet, Corn Bunting and Yellowhammer populations on our garden fat balls?

This matters because if we are primarily feeding garden birds for our own enjoyment, perhaps this can lead to a rethink about how we do it.

Maybe leaving your feeder empty for a few weeks or months doesn’t need to be something to feel guilty about, but is actually a good thing, reducing disease build-up and better mimicking the ephemerality of natural resources. We could tailor feeding to help threatened species, such as millet for House and Tree Sparrows, and not use foods that only benefit increasing species, such as peanuts for tits and woodpeckers. Those more able to access nature could stop feeding and allow those less able to continue to enjoy bringing the birds to them. We could reduce the number of feeders we have, and concentrate more on creating gardens with habitat for all wildlife, such as by making a pond, planting native flowers, shrubs and trees, letting our lawns grow wilder, and leaving or piling fallen leaves instead of blowing them away. We could donate some of the money we would have spent on bird food to land protection conservation charities instead.

Perhaps, overall, we just need to rethink bird feeding from an angle of ‘less is more’, where we get the benefits of interacting with birds but reduce the negative consequences. ■

References

• Broughton, R K, Shutt, J D, and Lees, A C. 2022. BB eye: Rethinking bird feeding. British Birds 115: 1 2-6.

Higher numbers of garden birds could have the effect of increasing their natural predators, such as Eurasian Sparrowhawk.

Research has shown that the disease Trichomonosis is spreading from Greenfinches to the Red-listed Hawfinch where the two species share feeders.

Blue Tit (left) – which is benefiting from garden feeding – outcompetes the Red-listed Willow Tit (right), which could be contributing to the latter’s decline.

There’s no doubt that feeding garden birds brings a lot of pleasure to a lot of people, and this is something to be encouraged – but in a way that benefits the birds, too.

Declining farmland birds such as Corn Bunting don’t benefit from garden feeding, but more targeted conservation measures could help them.