Identification of Farmland Bird Indicator Species for Practitioner Monitoring in the United Kingdom.

Agricultural intensification has resulted in bird population declines on farmland, with farmland bird specialists affected the most due their reliance on more traditional farming methods. Current voluntary breeding bird monitoring schemes across Europe require the observer to identify many species by sight and/or sound and often use complex survey methods and techniques, which might deter individuals from taking part. Indicator species provide a solution whereby only a few 'flagship' species need to be known to the observer, and these species indicate the status of the rest of the species within that taxon. Our aim was to determine if indicator species could be identified that correlated with the diversity or abundance of different bird communities present on farmland. We used breeding bird survey data collected on two Farmer Clusters, one in England and one in Scotland between 2021 and 2024. Using the 2021-2023 data, NMDS visualisation and further GLMM testing, several species were identified as potential indicator species. Corn Bunting, Linnet and Skylark were the species most strongly correlated with specialist farmland species' abundance, with Linnet showing a significant positive relationship against specialist farmland abundance and richness in both Farmer Clusters. In both Farmer Clusters, Goldfinch showed a positive significant relationship with total bird community species richness and abundance. The reliability of these indicator species was then tested against the 2024 data. Corn Bunting, Linnet and Skylark were again found to be significant when tested against specialist farmland abundance; while in England, Goldfinch and Stock Dove were significant when tested against total bird abundance. The farmland bird indicators identified here provide a much simpler list of species for a practitioner to learn to identify and survey and allow the surveyor to capture the overall diversity of farmland birds but also the status of the specialist communities.