Breeding bird population trends during 2013–2019 inside and outside of European badger control areas in England

Abstract

AbstractSince 2013, the Department for Environment, Food and Rural Affairs (Defra) has licenced culling of European badger (Meles meles) populations in several English regions. In the first 7 years, more than 100 000 badgers have been removed. It is critical to evaluate the ecological impact of severely depressing the population of a widespread predator from large areas of the country, such as effects on breeding bird populations. Citizen science survey data on the abundance of breeding birds supports the estimation of population trends, i.e. whether species are exhibiting population growth or declines, and the effects of potential environmental influences, such as badger removal, on these trends. Here, these survey data are used together with data on the presence and amount of culling in an area to explore whether removing badgers has an effect on breeding bird populations both inside and outside culling zones from 2013–2019. This is not equivalent to a controlled trial, but collects critical, landscape‐scale evidence in real‐world conditions. In analyses evaluating the effect of culling presence, 18 of 55 bird species showed significant or near‐significant growth rate changes. Of these, four species had higher growth rates and 14 exhibited lower growth rates in cull areas, compared to areas outside of the culling zones. When using culling intensity data to assess the impact on growth rates, 10 of 55 species showed significant or near‐significant results, with only one species exhibiting a higher population growth rate in the presence of more intensive culling. Predicted sensitivity to badger effects based on species' ecologies did not predict whether the measured relationships were significant, or their directions, suggesting that other factors underlie the patterns seen. Hence, there was little evidence to indicate consistent, community‐level effects of badger removal on bird populations. A landscape‐scale, quasi‐experimental approach is strongly recommended to provide stronger inference about the complex potential ecological effects of culling predators such as the badger.