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Feeding Wild Birds Reduces Insect Pests

11 April 2012

UK - The common British past-time of feeding wild birds has been shown to reduce local populations of insect pests, according to research published in Basic and Applied Ecology and funded via a Biotechnology and Biological Sciences Research Council (BBSRC) doctoral training award. The findings are of relevance not only to gardeners but also to agriculture, given that many common avian prey species are important crop pests.

Although the direct influence of providing food for wild birds in terms of bird survivorship has been studied, little had been done to understand wider consequences. Researchers from the University of Reading investigated the effects of feeding wild birds on the size and survivorship of colonies of pea aphid (greenfly) - a prey of many small passerine birds. The research was carried out in suburban gardens in Reading.

The researchers placed colonies of aphids in gardens with and without bird feeders. To account for amongst garden-variation, half of the colonies were left exposed to bird predation, while others were protected with a wire mesh as controls. After studying the aphid colonies over time, they found that exposed colonies in gardens with feeders had fewer aphids and shorter aphid colony survival times compared with the caged colonies. Gardens without feeders showed no such differences.

This is the first experimental evidence that feeding wild birds in domestic gardens can lead to significant reductions in local aphid abundance and colony survivorship.

Talking of the significance of her research, Melanie Orros said: "Our results show that by attracting birds into an area with supplementary food, a local increase in the natural prey consumed can be seen. It is an important finding because 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."

Pea aphids were chosen as they represent an important pest but further research would be needed to assess the impact on other species.

Miss Orros said: "Pea aphids are a useful start. The level of avian predation on pea aphids 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 if the depletion effect found here extends to other insects found around bird feeders."

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