We performed a laboratory experiment on caged, domesticated zebra finches to assess the effects of antimicrobial treatment applied to birds' plumage on the feather microbial loads of breeding pairs and their associated reproductive performance. Treatments included an experimental group that experienced frequent misting with a broad-spectrum antimicrobial, as well as two control groups. Microbial loads sampled from the belly feathers of breeders were higher post-hatching than pre-hatching, and experimental pairs had lower loads than controls at all sampled breeding stages.  Clutch size and hatching success did not differ among treatments, but experimental pairs fledged nearly 50% more offspring than controls due to experiencing much lower nestling mortality.  Offspring development rate varied among treatments: beak color scores sampled midway in the development of adult phenotype revealed that offspring of experimental pairs had more rapid development.  Findings imply that experimentally reduced density of feather microbial loads on breeders decreased reproductive costs in the post-hatch phase, resulting in increased offspring survival and condition.  At the time offspring fledged, uropygial gland volume tended to be greater among breeders that had experienced antimicrobial application throughout the breeding cycle.  These results are consistent with a growing literature showing that the feather microbiome contributes significantly to the evolution of avian life histories and behavior and indicate that zebra finches are a useful laboratory model for investigating in vivo effects of the feather microbiome on avian hosts.

The data were collected in an experiment on captive breeding zebra finches that were allowed to produce one clutch.  Belly feathers of breeding birds were swabbed at several reproductive stages for microbes, and samples were cultured on TSA plates. Microbial loads were measured as colony-forming units (CFUs).  Several measures of phenotype were taken on breeders and their offspring. Results were analyzed in STATA 15.

There are some missing values for uropygial gland size and CFU counts.