Pathogenic Bacteria Associated with the Feces of the Violet-Crowned (Ramosomyia violiceps) and Broad-Billed (Cynanthus latirostris) Hummingbirds in Disturbed Forest and an Urban Environment in West-Central Mexico.

Abstract

Human activities, such as habitat fragmentation, have displaced wild birds into urban and agricultural areas, increasing their exposure to enteric pathogens through contaminated food and water. Molting stress further heightens their susceptibility to infection. This study examined 1) the presence of Klebsiella pneumoniae, Salmonella enterica serovar Typhimurium, Listeria monocytogenes, and Campylobacter jejuni in fecal samples from Violet-Crowned (Ramosomyia violiceps) and Broad-Billed (Cynanthus latirostris) Hummingbirds across two environments: disturbed forest and urban; 2) potential associations with contamination sources (wastewater, rivers, water bodies, and livestock feces); and 3) the effects of molting. Fecal samples were analyzed using real-time PCR and Bayesian generalized linear mixed models to evaluate five response variables: individual pathogen presence [corresponds to the 3 pathogens (K. pneumoniae, S. enterica, and L. monocytogenes)], combined pathogen presence, and pathogen copresence. Predictors included hummingbird species, molt, environment type, and distance to contamination sources. Of the bacteria, K. pneumoniae exhibited the highest prevalence (46%), followed by S. enterica (9.5%) and L. monocytogenes (7.9%); C. jejuni was not detected. Results indicated that 1) R. violiceps had approximately threefold higher odds of K. pneumoniae presence than C. latirostri and 2) molting individuals had 6.5-fold higher odds of carrying at least one pathogen. Neither environment type nor distance to contamination sources showed significant effects. The high prevalence of K. pneumoniae highlights the urgent need to preserve natural habitats and reduce anthropogenic pressures on wild bird populations. Molting increases susceptibility to gastrointestinal pathogens, while species-specific differences suggest variable resistance mechanisms. These findings underscore the importance of 1) habitat conservation to minimize pathogen exposure, 2) urban green space management with strict hygiene protocols for artificial feeders, and 3) integrated wildlife pathogen surveillance within One Health frameworks.