Synthesis of Anthropogenic Impacts on Birds - Systematic Map and Bibliometric Analysis of Meta-Analyses

Renato Vidić , Marion Chatelain, Olivia M. Smith, Marta Szulkin, Danijela Zanko , Nicole Lussier, Ayumi Mizuno , Davide Michelangelo Dominoni, Marcel E. Visser , Shinichi Nakagawa , Antica Culina

Anthropogenic environmental change is a major driver of global bird declines, affecting species across continents, ecosystems, and life-history strategies. As such, it has drawn much attention in both primary research studies and meta-analyses. Because meta-analyses influence scientific consensus and conservation policy, it is essential to evaluate the representativeness and transparency of this evidence. However, despite the growing number of meta-analyses , these aspects have never been assessed, creating a clear need for a comprehensive global evaluation of meta-analyses on anthropogenic impacts of birds. Here, we present the first global synthesis, including 149 meta-analyses of anthropogenic influences on birds. We analyzed their thematic, taxonomic, ecological, and geographic coverage, evaluated adherence to reporting and methodological standards, and assessed research production, collaboration, and societal visibility using bibliometric and altmetric approaches. Meta-analyses addressed a wide range of anthropogenic pressures and birds’ responses, however with uneven attention to different topics. Habitat loss and fragmentation, agriculture, and urbanisation were overrepresented across studies, while light and noise pollution, invasive species, and hunting were largely neglected. Responses focused mainly on species abundance, diversity, and reproduction, with limited attention to behaviour, movement, migration, or phenology. Taxonomic coverage was biased towards Passeriformes, and geographic coverage skewed toward North America and Europe. Reporting standards were not widely followed, and almost half of the meta-analyses would not be possible to repeat or update. Almost none of the meta-analyses were preregistered or estimated risk of bias in primary studies, though most controlled for non-independence, and tested for publication bias. Bibliometric and altmetric analyses revealed high collaboration but geographic imbalance among authors. Overall, meta-analytical research on anthropogenic impacts on birds is extensive - but thematically, taxonomically, ecologically, and geographically uneven, with suboptimal transparency. Addressing these limitations is crucial to improve the reliability, comparability, and policy relevance, ultimately supporting more effective conservation strategies for birds.