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Bacillus licheniformis, a soil bacterium capable of degrading the b-keratin in feathers, is present in the plumage of some wild-caught birds, but the published carriage rate is quite low. Microbial degradation could be a selective agent leading to the evolution of molt and plumage pigmentation, but we hypothesized that for B. licheniformis to have played an important role in avian evolution, it is likely to occur more widely in bird populations than previously reported. We sampled the plumage of 461 wild-caught birds of eight species. We designed a selective and differential culture method to isolate bacteria with the potential to degrade feathers. Putative feather-degrading bacteria were isolated from 21-59% of the individuals of each of the species tested, for an average carriage rate of 39%. 16S rRNA (rrnA) sequencing of 98 of these bacterial isolates indicated that 69% were Bacillus lichenformis, suggesting that the prevalence of this feather-degrading bacterium is 4 3 higher than previously reported. We also hypothesized that interspecific variation in avian plumage, behavior, and habitat may have led to the evolution of host-specific B. licheniformis strains. Fingerprinting of B. licheniformis isolated from Northern Saw-whet Owls (Aegolius acadicus) and Gray Catbirds (Dumetella carolinensis) using REP-PCR demonstrated that for nine owls, one individual carried four different strains and eight individuals carried only one strain. Of 20 catbirds, there was a single strain found on nine birds, but four carried two different strains each. SINOPSIS. Prevalencia y diversidad genetica de Bacillus licheniformis en el plumaje de aves