Associations Between Plant-Derived Diet Composition and Fecal Microbiota in Wintering Common Cranes in the Yellow River Estuary

The gut microbiota is closely linked to nutrient metabolism and host health in birds, but whether variation in plant-derived diet composition is accompanied by corresponding gut microbiota variation during winter remains unclear. In this exploratory study, we analyzed 150 fecal samples from five groups of wintering Common Cranes (Grus grus) in the Yellow River Estuary during the 2025/2026 wintering season. Plant DNA metabarcoding and 16S rRNA sequencing were used to characterize the plant-derived diet composition, fecal microbiota, and predicted microbial functions. Both plant-derived diet composition and fecal microbiota structure differed significantly among groups. Groups J1 and J2, sampled concurrently in January, differed markedly in plant-derived diet composition, whereas overall fecal microbiota separation and differences in most predicted functions were relatively limited. Five plant family–bacterial genus associations passed FDR correction without sampling-group adjustment, but none remained significant after adjustment. Overall, plant-derived diet composition and fecal microbiota both varied across the sampled groups, but their patterns of differentiation were not fully concordant. Because sampling time and site were not fully crossed, these patterns cannot be attributed to diet alone. These findings support considering farmland foraging habitats in the management of wintering Common Cranes, with attention to food resource availability throughout winter.