We conducted a short experiment a couple of years ago to test the assertion that avian uropygial gland secretions are spread onto the plumage during the act of preening at least in part to keep feather-degrading bacteria within bounds. However, this function of the preen oils was tested mostly in vitro. Aviary house sparrows (Passer domesticus) were either glandectomized (surgical gland removal) or sham-operated (control). Glandectomy served to deprive birds from coating their plumage with oils that might block keratinolytic or feather-associated bacteria. We found that the change (post- minus pre-treatment) in the abundance of feather-degrading bacilli was not significant after one month, while that of other cultivable bacteria substantially increased in the glandectomized birds. We discuss the sanitation function of the gland oils and the possible sources of discrepancy between previous in vitro and our in vivo results.
Our study was submitted to Naturwissenschaften and now has a ‘moderate corrections needed’ decision.
Czirják GÁ, Pap PL, Vágási CI, Giraudeau M, Mureșan C, Mirleau P and Heeb P. Preen gland removal affects the abundance of feather-associated bacteria in house sparrows (Passer domesticus).