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Recent studies in humans have shown that certain pesticides could affect the composition and functions of gut microbiota, an essential modulator of vertebrate physiology, leading to potential dysbiosis. However, this relationship remains largely unknown in wild birds despite the implications of pesticides in the current decline of farmland species. The present study sought to fill this gap by providing data on the association between pesticide concentrations in blood and gut microbiota characteristics in relation to individual traits in a farmland raptor, the Montagu’s harrier ( Circus pygargus ). Results showed that females with higher body condition and higher pesticide load harboured a higher gut bacterial richness and diversity, while the relationship was opposite in males with higher body condition. Regarding taxonomic composition, Proteobacteria was the main phylum found in all nestlings. Differences in certain phylum and genus abundance according to pesticide load were found, with more Bacteroidota, Leifsonia and less Bulkholderia in nestlings with higher pesticide concentrations in their blood. Thus, this study highlights differences in microbiota and contamination by several pesticides according to the phenotypic characteristics of a wild raptor, and shows that farmland birds can represent relevant biosentinels for assessing the health/proper functioning of ecosystems (One Health approach). • Pesticides may impact gut microbiota structure. • 36 compounds of pesticides were detected in blood of Montagu’s harrier chicks. • Microbial diversity shifts were related to pesticide load, sex and body condition. • Proteobacteria were linked to lower pesticide load, Bacteroidota to higher levels. • Farmland birds may serve as bio-sentinels in ecosystem health monitoring.
Bariod et al. (Wed,) studied this question.