ABSTRACT Gut microbiomes play a crucial role in host physiology and seasonal adaptation. While seasonal shifts in avian gut microbiota are often attributed to seasonal diet variation, environmental factors may be equally or more important, particularly in urban ecosystems. This study aimed to determine whether seasonal variation in the gut microbiome of free‐living feral pigeons ( Columba livia f. domestica ) inhabiting urban environments is associated with seasonal changes in diet and environmental conditions. We captured feral pigeons at three locations in Groningen, the Netherlands, during winter (January–February 2019) and summer (July–August 2019). Cloacal swabs and fecal samples were collected to assess gut microbiota via 16S rRNA sequencing and diet via DNA metabarcoding, respectively. Microbial diversity and composition showed significant seasonal variation and location effects. At Vismarkt, one of the three urban sampling sites within the city of Groningen, Firmicutes were more abundant in summer than in winter, while Actinobacteria were more abundant in winter. Dominant genera also varied seasonally, with Lactobacillus more abundant in summer. In contrast, the diet composition was dominated by Poaceae (grasses), Fabaceae (legumes), and Asteraceae (daisies) across all seasons and locations, with no detectable differences between locations or seasons. Distance‐based redundancy analysis indicated that temperature was significantly associated with microbiome composition, whereas diet as measured here showed no detectable association. This suggests that seasonal microbiome variation in urban feral pigeons may be related to seasonal environmental conditions even without detectable dietary shifts, consistent with the idea that seasonal environmental conditions can contribute to microbiome seasonality in birds.
Zhang et al. (Fri,) studied this question.