Data from: Species-specific and microbial variability in the antimicrobial efficacy of uropygial secretions in wild passerines

Uropygial secretions are thought to play an antimicrobial role in birds,
but few studies have compared their effectiveness across multiple species
and microorganisms using standardized methods. We evaluated the
antimicrobial activity of uropygial secretions from 212 individuals of 11
passerine species in southwestern Spain, testing their inhibitory effects
against Bacillus licheniformis, B. subtilis, Candida albicans, Escherichia
coli, and Salmonella typhimurium by flow cytometry. Antimicrobial activity
varied significantly among species and microorganisms: house sparrows
(Passer domesticus) consistently exhibited stronger and broader responses,
whereas activity against S. typhimurium was generally low. Phylogeny,
migratory status, and social behavior did not explain variation, but
uropygial gland size was positively associated with antimicrobial activity
both globally and in some bird species. Body condition exhibited
species-specific associations with antimicrobial activity, showing
positive correlations in some bird species and negative correlations in
others. Overall, our findings highlight the uneven distribution of
antimicrobial defenses among passerines and underscore the importance of
comparative, chemically informed, and methodologically standardized
approaches to clarify the ecological and evolutionary significance of
uropygial secretions.