New research has shown that feeding wild birds reduces insect pests in gardens, according to a report in Basic & Applied Ecology.
Funded via a Biotechnology & Biological Sciences Research Council doctoral training award, researchers from the University of Reading investigated the effects of feeding wild birds on the size and survival of pea aphid (greenfly) colonies - a prey of many small birds.
The research was carried out in suburban gardens in Reading. Colonies of aphids were placed in gardens with and without bird feeders. Half of the colonies were left exposed to bird predation, while others were protected with a wire mesh as controls.
After studying the colonies over time, the team found that those exposed in gardens with feeders had fewer aphids and shorter colony survival times compared with the caged colonies. Gardens without feeders showed no such differences.
Researcher Melanie Orros said this is the first experimental evidence that feeding wild birds in domestic gardens can lead to significant local aphid reductions and colony survival.
"Our results show that by attracting birds into an area with supplementary food, a local increase in the natural prey consumed can be seen. We increasingly need to consider a variety of sustainable methods and means to control pest populations. This could have important implications in agriculture and in our gardens."
Orros added: "Pea aphids are a useful start. The level of avian predation was used as a proxy for the potential for biological control on farms in a recent Europe-wide study, for example.
"However, whereas aphids are seen as pests, many insects are regarded positively because they are pollinators or consume other pests. It would therefore be of interest to test whether the depletion effect found extends to other insects around bird feeders."
Experts welcome evidence of feeders' role in predator encouragement
Dr Nick Carter, Former development director, British Trust for Ornithology
"Although many birds eat aphids, the reproductive capabilities of the latter during most of the year - giving birth to live young without the need for sexual reproduction - would outstrip predation. These results indicate otherwise and show that feeding birds in spring and summer gives the gardener a benefit. The birds are staying, even when they are not taking from feeders. Pea aphids are large, so worthwhile for the birds to feed on. It also shows the effects when predators such as ladybirds, spiders and ground beetles as well as fungal diseases had access to the aphids. The reduction in numbers and colony longevity might not feed through to a significant yield benefit."
Jane Lawler, marketing director, Gardman
"On first sight it looks like very good news for gardeners and further evidence that encouraging wildlife into the garden can only be a good thing."