Direct and indirect effects of pesticide exposure on farmland raptor gut microbiota

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 were 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).