Animals generally benefit from their gastrointestinal microbiome, but the factors that influence the composition and dynamics of their microbiota remain poorly understood. Studies of nonmodel host species can illuminate how microbiota and their hosts interact in natural environments. We investigated the role of migratory behaviour in shaping the gut microbiota of free‐ranging barn swallows (Hirundo rustica) by studying co‐occurring migrant and resident subspecies sampled during the autumn migration at a migratory bottleneck. We found that within‐host microbial richness (α‐diversity) was similar between migrant and resident microbial communities. In contrast, we found that microbial communities (β‐diversity) were significantly different between groups regarding both microbes present and their relative abundances. Compositional differences were found for 36 bacterial genera, with 27 exhibiting greater abundance in migrants and nine exhibiting greater abundance in residents. There was heightened abundance of Mycoplasma spp. and Corynebacterium spp. in migrants, a pattern shared by other studies of migratory species. Screens for key regional pathogens revealed that neither residents nor migrants carried avian influenza viruses and Newcastle disease virus, suggesting that the status of these diseases did not underlie observed differences in microbiome composition. Furthermore, the prevalence and abundance of Salmonella spp., as determined from microbiome data and cultural assays, were both low and similar across the groups. Overall, our results indicate that microbial composition differs between migratory and resident barn swallows, even when they are conspecific and sympatrically occurring. Differences in host origins (breeding sites) may result in microbial community divergence, and varied behaviours throughout the annual cycle (e.g., migration) could further differentiate compositional structure as it relates to functional needs.

中文翻译：

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迁移，病原体和鸟类微生物组：同胞移民和居民的比较研究

动物通常会从胃肠道微生物组中受益，但是影响其微生物群组成和动力学的因素仍然知之甚少。对非模型宿主物种的研究可以阐明微生物群及其宿主在自然环境中如何相互作用。我们通过研究秋季迁徙期间在迁徙瓶颈处同时出现的迁徙和居民亚种，研究了迁徙行为在塑造自由散养的燕子（Hirundo Rustica）肠道菌群中的作用。我们发现宿主内微生物丰富度（α-多样性）在移民和居民微生物群落之间是相似的。相比之下，我们发现，就存在的微生物及其相对丰度而言，各组之间的微生物群落（β-多样性）存在显着差异。在36个细菌属中发现了成分差异，其中27个细菌在移民中表现出更高的丰度，而9个在居民中表现出更高的丰度。支原体种类丰富。和棒杆菌spp。在移民中，这是其他有关迁徙物种研究所共有的模式。对主要区域病原体的筛查表明，居民和移民均未携带禽流感病毒和新城疫病毒，这表明这些疾病的状况并不构成观察到的微生物组组成差异的基础。此外，沙门氏菌的流行和丰富根据微生物组数据和培养分析确定的spp。在各组中均较低且相似。总体而言，我们的研究结果表明，迁徙性和常驻性燕子的微生物组成不同，即使它们是同种的并同伴发生的。寄主来源（繁殖地点）的差异可能导致微生物群落分化，并且在整个年度周期内行为的变化（例如迁移）可能会进一步区分组成结构，因为它与功能需求有关。