Installing bird nest boxes improves pest control in cider apple crops

Research by the University of Oviedo and SERIDA (Asturias Regional Agrifood Development Service) shows the benefits of installing nest boxes for insectivorous birds in Asturias’ cider apple orchards.

Combining a large-scale experiment and careful field observations, researchers have found that birds nesting in the boxes capture large quantities of arthropods to feed their chicks, thus reducing the incidence of insect pests among the apple trees. Based on the conclusions from the study, published in Journal of Applied Ecology, the researchers recommend that nest boxes be encouraged as a measure to control pests effectively, cheaply and in an environmentally friendly way.

“Our aim was to provide farmers with tools to intensify environmentally friendly measures – that is, to give them ways of maintaining productivity by promoting the ecosystem services that biodiversity brings,” says Daniel García, biologist and professor of ecology at the University of Oviedo, and co-author of the study with Marcos Miñarro and Rodrigo Martínez-Sastre, also biologists and researchers at SERIDA.

Miñarro explains that “nest boxes have always been seen as a way of attracting insectivorous wild birds and encouraging their ecological role but, paradoxically, there was hardly any information about their usefulness in regard to agricultural crops”.

The researchers installed more than 100 nest boxes in 12 different orchards, and confirmed that the birds occupied almost a third of them, and across all the orchards. Comparing these orchards with equivalent ones without boxes, they assessed the insecticidal effect of the nesting birds. To do this, they estimated the birds’ attack on green plasticine decoys that simulated apple tree caterpillars. They also counted the number of insects, both in the trees around the occupied boxes and in equivalent trees in orchards without boxes.

Both methods demonstrated greater pest control on orchards with nest boxes than on those without them. Equipped with cameras and telephoto lenses, the biologists were able to photograph the adult birds as they entered the boxes, carrying food in their beaks to feed their chicks. By doing this, they were able to classify the insects caught by different species of birds. They identified the blue tit as the most effective pest-controlling species, as insects such as the apple blossom grub and the rosy apple aphid constituted a quarter of their prey.

By installing nest boxes in the apple orchards benefits not only the cider apple crop, but also the birds, which have a wider range of suitable places to build their nests. Apple producers who decide to give up using chemical pesticides and install nest boxes have access to a new line of subsidies from the Asturias regional government, as part of the Common Agricultural Policy, specifically aimed at promoting biodiversity in cider apple orchards, and inspired by the findings of this research team.

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García, D., Miñarro, M., & Martínez-Sastre, R. (2020). “Enhancing ecosystem services in apple orchards: nest boxes increase pest control by insectivorous birds”. “Journal of Applied Ecology” 00:1-11. https://doi.org/10.1111/1365-2664.13823