allopreening

Allopreening is a social grooming behavior in which one bird uses its bill to groom or preen the feathers of another individual. It is a form of allogrooming and is most commonly observed in social or pair-bonded species, including many waterfowl, parrots, corvids, and penguins. It is distinct from self-preening, which a bird performs on its own body.

During allopreening, the donor bird runs its beak along the recipient’s feathers, often applying preen oil from the uropygial gland to condition the plumage. The behavior can be reciprocal, with both birds taking turns, or unilateral. Its frequency and pattern are influenced by social relationships: bonded mates, kin, and stable group members typically engage more in allopreening, which helps maintain affiliation and cooperation.

The functions of allopreening are multiple. It aids parasite control and feather maintenance, assists in the distribution of preen oil to condition plumage, and helps align feathers. Socially, it reinforces bonds, reduces aggression, and can serve as a reconcile-after-conflict signal, indicating affiliative intent.

In wild populations, allopreening is associated with reduced stress and greater cooperation in activities such as defense of territory or parental care. In captive settings, it often reflects social compatibility. While generally beneficial, allopreening can carry risks of parasite or pathogen transmission when nonrelated or stressed individuals interact frequently.