Anting (behavior)

A brahminy kite anting at lalbagh Botanical Garden in Bangalore, India

Anting most commonly occurs on the ground but in some species, birds practice anting on tree branches. A bird will place the tip of its wing on the ground and rub its bill containing an ant from the tip of the wing up.[1] The tail is usually tucked between the legs and under the body, which results in the bird being unstable. Birds use one ant at a time and only rub a feather once with an ant. However, there are some cases where an ant is used more than once but never exceeds three uses.[1] There are some exceptions to this as starlings often take a ball of ants in their bills to be used for anting. Active anting happens very quickly and can often be mistaken for regular feather maintenance. This type of anting can last anywhere from just several minutes to half an hour. Most species of birds practice active anting and do this individually or in small groups. Birds may also use 'substitutes' in active anting. Birds have been seen to use snails, grasshoppers, amphipods and even larvae.[1]

Passive anting occurs when a bird rubs its wings and tail on an anthill. Once a bird has found an anthill it will then spread both of its wings forward at the same time. It will then sit on its tails which attracts the ants. Once the ants are on their wing feathers they provoke the ants by rubbing their head or beak through their feathers where the ants are. To prevent ants from crawling onto a bird's head or beak the bird will shake its head very quickly. The birds allow the ants to roam freely around its feathers. This type of anting is less common and is mostly seen in robins and ravens.[1]

Anting to get rid of ectoparasites is another hypothesis for anting in songbirds. This hypothesis suggests that birds use the chemical secretions that come from ants to control and rid of parasites in their feathers. Microorganisms such as bacteria and fungi can destroy a bird's feathers if their numbers get large enough. Formic acid is a commonly produced chemical by ants, and it was found to inhibit growth of feather destroying microorganisms.[3] However, there is little evidence that chemicals from ants help to remove or deter other parasites such as feather lice and mites.[3]

A Black woodpecker anting in Hungary

The hypothesis that anting is a form of feather maintenance suggests that anting brings saliva to the bird's feathers for use in preening. This helps to remove old preen oil and other substances.[4]

The food preparation hypothesis suggests that birds rub the ant in its feathers to remove a substance on the ant. Ants produce formic acid as an anti-predator adaptation. Thus, when an ant feels threatened, as when in the beak of a bird, it will spray formic acid. It is suggested that birds then rub the ants in their feathers to remove the harmful formic acid. The bird will then ingest the ant. This can be seen in European starlings, Sturnus vulgaris.[5]

Anting has been compared to human activities such as smoking and other external stimuli that serve no biological purpose and is just for self-stimulation. This hypothesis has been suggested as anting has no obvious function, it is non-adaptive, birds are said to achieve pleasure from anting and anting has characteristics of a habit. However, there is no definitive evidence that sensory self-stimulation is the purpose of anting in birds. There have been several studies that claim to prove this hypothesis while others say just the opposite.[6]

It has been found that passerine birds molt in the summer months. These birds often focus much of the anting on their wings and tails. This is where the largest feathers emerge, and it has been suggested that anting helps stimulate the growth of these feathers during molt. Not all birds that ant do so during molt.[4]