Apparent anti-parasite behaviour in the Norfolk Island green parrot Cyanoramphus cookii

Birds must cope with all manner of ectoparasites, from insects and mites to bacteria and fungi. During their grooming routine, several Norfolk Island green parrots Cyanoramphus cookii were observed and photographed, and a pair was videoed, biting off and chewing small pieces of lateral shoot and bark of pepper trees Piper excelsum and working the chewed material through their feathers. They also stripped the leaves and rubbed their beaks along the branches before extracting preen oil. Pepper trees are a well-known source of piperine and other potent aromatic chemicals that are insect repellent and antimicrobial. This appears to be a rare example of a bird using plant material to anoint themselves, which we interpret as a way to repel blood-sucking insects and ectoparasites and, possibly, void endoparasites, thereby improving fitness.