Many birds engage in anting, a behaviour in which a bird approaches a colony of ants (small insects), picks up ants with its beak, and rubs the ants on its feathers. Since ants instinctively defend themselves by spraying formic acid, the bird ends up with formic acid on its feathers and skin. There are several theories about the possible benefit that birds get from anting.
Relief of Skin Irritation during Feather Change
Anting behaviour typically takes place during the summer. This fact leads some scientists to believe that the function of anting is to relieve skin irritation that birds feel, especially during summer months. In summer, birds lose old feathers and grow new ones. The formic acid, which the birds apply to their feathers and skin through anting, may act as a kind of skin lotion, helping to soothe the skin irritation caused by feather loss and replacement.
Protection against Parasites
Another theory is that the formic acid helps the birds protect themselves from external parasites, such as mites and ticks, that can infest their feathers or skin. In anting so the theory goes a bird is essentially using the formic acid that it spreads over its feathers and skin as a chemical defence against parasites.
Food Preparation
A third theory is release of formic acid makes it possible for the birds to feed on the ants. Formic acid tastes bitter; if the birds provoke ants into releasing the formic acid, the bitter taste is removed from the ants’ bodies and the birds can feed on the ants without tasting the bitterness. So, according to this theory, anting is just a way for birds to make sure the ants taste good.