Bird-mediated damage in English vineyards is modest and spatially structured, with no detectable effect on yield

Biodiversity in agricultural landscapes provides both ecosystem services and disservices, and understanding its net effect on production is essential for sustainable management. Birds are often perceived as pests in fruit-growing systems, but their overall impact is context-dependent. Viticulture is expanding in the United Kingdom, where bird-mediated grape damage is considered a challenge. Here, we assessed the effect of birds on production across English vineyards spanning gradients of landscape complexity and management practices. We combined grape damage assessments, experimental exclusion and bird surveys to quantify bird-mediated grape damage and relate it to yield. Overall, bird damage was modest (3.8% per bunch) and strongly spatially structured, peaking at around 20% damage per bunch at the field edge and declining to ~5% at 40 m from the edge. Damage was not related to the abundance of grape-eating bird species, and varied substantially among sites and years. Damage increased with semi-natural habitat cover and ground vegetation, but showed no relationship with wooded edges, suggesting that habitat structure and easy access into the crop, rather than habitat type or abundance, underpin frugivory patterns. Importantly, our models showed no correlation between bird-mediated grape damage and yield, which instead varied markedly between management approaches (51% lower yield in organic vineyards) and years (27%). These findings suggest that bird communities do not impose significant production costs in English vineyards, and that biodiversity conservation is compatible with production. More broadly, our results highlight the importance of distinguishing species presence from functional impacts, and the importance of considering ecological and management impacts when assessing yields.