Experimental study of the effect of preen oil against feather bacteria in passerine birds.

Avian plumage harbors various pathogens such as feather-degrading bacteria, which have the potential to reduce host fitness. A growing body of evidence suggests that the secretion of the uropygial gland of birds-preen oil-acts as one of the first lines of defence against harmful bacteria. However, previous studies on the antimicrobial impact of preen oil have yielded controversial results.

Manipulation of parental effort affects plumage bacterial load in a wild passerine.

It has been suggested that plumage microorganisms play an important role in shaping the life histories of wild birds. Some bacteria may act as pathogens or cause damage to feathers, and thereby reduce individual fitness. Intense parental care in birds can result in a reduction of self-maintenance and preening behavior in parents and therefore might affect the dynamics of microbiota living on their feathers.