Gut microbiota of buzzard nestlings

Exploring the dynamics of gut microbiome colonisation during early-life stages is important for understanding the potential impact of microbes on host development and fitness. Evidence from model organisms suggests a crucial early-life phase when shifts in gut microbiota can lead to immune dysregulation and reduced host condition. However, our understanding of gut microbiota colonisation in long-lived vertebrates, especially during early development, remains limited. We therefore used a wild population of common buzzard nestlings (Buteo buteo) to investigate connections between the early-life gut microbiota colonisation, environmental and host factors. We targeted both bacterial and eukaryotic microbiota using the 16S and 28S rRNA genes. Longitudinal data analysis revealed that age significantly affected microbial diversity and composition. Nest environment was also a notable predictor of microbiome diversity and composition, with particularly eukaryotic communities differing between habitats occupied by the hosts. Nestling condition explained microbial community composition, while Leucocytozoon infection was associated with microbial beta diversity. These findings emphasise the importance of studying microbiome dynamics to capture changes occurring during ontogeny and the potential confounding effects of age. They highlight the role of microbial communities in reflecting host health and the importance of the nest environment for the developing chick microbiome. Overall, this study contributes to understanding the complex interplay between microbial communities, host factors, and environmental variables, and sheds light on the mechanisms governing gut microbial colonisation during early-life stages.