1.6 - PREENING AND BATHING
Preening is the act of cleaning- and keeping the feathers in good condition. Parrots mostly preen their feathers by carefully using their beak. Many parrot species have a gland (the uropygeal gland) just above the base of the tail feathers that produces a special oil. You will sometimes observe parrots spreading this oil in their feathers using their head and beak during preening. The exact function of the oil isn't known, but it's believed to help keep the feathers clean and free from disease-causing pathogens, aid in repelling moisture, as well as contributing to the formation of vitamin D when birds are exposed to UV light. In some species, like parakeets, the secretions from the uropygeal gland is thought to play a part in mate selection and possibly other social behaviors.
Parrots will most often preen themselves right before they settle in to rest, or as they transition from resting to other activities. We can sometimes also observe parrots rousing their feathers and preening after they have been spooked or otherwise experienced a high level of arousal, as they are calming down. Sometimes, preening and scratching will occurr in contexts where we wouldn't expect to see it at all, like in the middle of a conflict. This is sometimes called "displacement behavior."
This lorikeet is very aroused, and starts preening itself in the middle of a conflict with another bird.
Allopreening is the term for when parrots preen each other. Parent birds will preen their young, and bonded birds will preen each other. In adults, allopreening mostly occurs on the neck and head, where parrots can't reach to preen themselves. This is likely both something that benefits the birds by keeping their feathers in good condition, and it can also strenghten the bond between two individuals. (And it definitely looks like it feels pretty good!)
Bathing and showering
Bathing and showering in water is normal behavior for parrots. Unlike many other birds, parrots do not tend to sand- or dust bathe. How often a parrot will bathe or shower and what style it uses, bathing in pools or water or showering in rain, differs between species and individuals can differ in their preferences. Some smaller birds tend to like "bathing" in wet foliage or salad. All parrots have very distinct behavior patterns when bathing or showering. They will fluff up their feathers to allow water to get in, hold their wings out from their bodies and engage in various motions to cover their feathers and bodies in as much water as possible. In other words, it's very clear when a parrot is in the mood for a getting wet and when it is not. A bird that is not keen on getting wet will often run away from the water source or sit perfectly still with tight feathers, so that very little water can get in under the feathers.
References and further reading:
Murphy, Braun & Millam, Bathing behavior of captive Orange-winged Amazon parrots (Amazona amazonica)
Applied Animal Behaviour Science 2011, 132; 200-210