Community-level physiological profiles of cloacal microbes in songbirds (order: Passeriformes): variation due to host species, host diet, and habitat.

The relationship between microorganisms and birds has received increased attention recently. The state of knowledge of this relationship, however, is based largely on examination of sick or dead birds, and knowledge of the prevalence and community structure and function of microbes in healthy wild populations is limited. Using carbon substrate utilization profiles, microbial communities were examined in 91 cloacal samples from 14 species within apparently healthy summer and winter passerine populations. Within each season, gradient lengths and eigenvalues from ordination analyses suggested that many samples differed in their carbon substrate utilization and several had very different communities. Cloacal microbe carbon utilization profiles were distinguishable among host species, season-specific diet, and study site in the ordination analyses. However, these patterns were only observed for the analysis of the summer data set. The results of this study support the idea that the avian host's microbial community, relative to carbon substrate utilization, is related to host diet. Previously, this pattern had only been reported for potential pathogens isolated from the avian cloaca. Study site-specific patterns in the ordination analysis suggest that environmental conditions at a particular study site may influence cloacal microbial communities in birds. Results of this study indicate that examination of community-level physiological profiles may be a useful technique for distinguishing among avian cloacal samples, similar to that already established for discriminating aqueous and soil samples. Future studies that correlate microbe physiological profiles to condition-based indices of avian hosts may be most useful for eventually using the profile as an indicator of environmental conditions experienced by hosts.