Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Various bird species feed on a variety of insects, ticks and other external parasites, dead and wounded tissue, clots and blood, secretions and organic debris found on the body of other vertebrates (hosts or clients). Herein I present an overview of so called cleaner birds based on literature records, field observations, and photo surveys. I found that 101 bird species in 32 families practice cleaning even if some of them do so very occasionally. Cleaner birds range from the renowned Red-billed Oxpecker Buphagus erythrorhynchus from Africa to the little known Crested Partridge Rollulus roulroul from Malaysia. Clients are mostly medium-sized to large herbivores such as iguanas, tortoises, capybaras, and wild and domestic ungulates, but also include carnivores such as seals and seabirds. Some clients adopt particular, posing postures while being cleaned, whereas others are indifferent or even disturbed by the activity of some cleaner species. Capybaras, giant tortoises and iguanas are among the posing clients, whereas most ungulates remain oblivious to cleaners. Features such as omnivorous diet and/or opportunistic behaviour, and the habit of associating in other ways with larger vertebrates are related to cleaning behaviour. Most cleaner birds inhabit open areas, and forest-dwelling cleaners seemingly are few.1913247Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)