Complementary, not competing: passive acoustic monitoring and point counts reveal different facets of bird communities in agricultural landscapes

Abstract

Reliable, scalable monitoring of declining bird communities is essential for evaluating conservation management. We compared species richness and community composition derived from passive acoustic monitoring (PAM) with those from traditional point counts in 11 winter wheat fields under pesticide-free agri-environment schemes (AES) versus conventional management, in Saxony-Anhalt, Germany. Additionally, we measured landscape complexity and field size. We paired both survey methods and validated automated detections against an independent blind-listening reference. Furthermore, we classified species according to functional traits, including habitat preference, trophic niche, body mass, and hand-wing index. A validation index combining the top-5% mean confidence and temporal coverage achieved an ≈ 84% expert-confirmation rate.PAM detected more species than point counts, averaging 74% higher species richness, while between-method overlap remained substantial. Nonmetric multidimensional scaling indicated partial separation by survey method and lower dispersion for PAM, consistent with more uniform communities under standardized sampling. Environmental vector fitting identified management regime (pesticide-free AES vs conventional) as the strongest correlate of community composition, whereas landscape complexity and field size had no significant effect. Method-specific responses to environmental gradients were similar: field-level richness rankings were congruent, and community-weighted traits differed little, aside from a modest shift toward open-habitat species in point counts. These results indicate that PAM increases total detections without altering the fundamental ecological signal captured by point counts. We recommend a hybrid workflow combining broad PAM networks with targeted point counts to deliver accurate, transparent, and scalable monitoring of AES as well as indicators for biodiversity assessments.