Crows are highly intelligent, adaptable birds with a remarkably varied diet, and they do consume ants. As omnivores, crows opportunistically eat nearly anything, from seeds and fruit to small vertebrates and carrion. However, the connection between crows and ants involves a curious behavior known as anting. This unique ritual involves the deliberate application of ants to the bird’s plumage, suggesting a purpose beyond mere nutrition. Scientists believe this behavior serves a biological function more akin to self-medication than a meal.
Ants as a Minor Dietary Component
Ants are typically a supplementary food source for crows, providing a boost of protein when larger prey or preferred foods are scarce. Crows usually favor bigger insects like beetles or grasshoppers, but they will not ignore an easy concentration of ants. They may target anthills and consume adult worker ants, or more commonly, the protein-rich ant larvae and pupae, often called “ant eggs.”
This consumption is generally an act of convenience, fitting into the crow’s broad foraging strategy. Because of their small size, a crow must consume a large volume of ants to gain significant caloric benefit. Therefore, the nutritional intake from ants is considered a minor component of the overall diet, unlike contributions from seeds or larger animal matter. The sheer abundance of ant colonies makes them a readily available food source for a foraging crow.
The Unique Practice of Anting
The most unusual interaction between a crow and an ant is not ingestion, but a maintenance behavior called anting. This deliberate action encourages the ant to release its defensive chemicals onto the bird’s feathers. Scientists have documented two distinct forms of this behavior, categorized by the crow’s level of direct involvement.
Active Anting
“Active anting” occurs when the crow carefully picks up an ant in its beak and rubs the insect repeatedly over its flight feathers, tail, and skin. The crow often adopts a contorted posture, tucking its head and twisting its wings to allow the ant access to hard-to-reach areas. The ant is typically held just long enough for it to spray its chemical defense before the crow discards or occasionally swallows it.
Passive Anting
“Passive anting” involves the crow lying directly on an ant nest or area of high ant concentration. The bird spreads its wings and tail, allowing the insects to crawl freely through its plumage. This posture encourages the ants to swarm over the feathers in response to the disturbance. This non-combative exposure suggests the crow is seeking the chemical secretion the ants produce, rather than the insect itself.
Scientific Explanations for Anting Behavior
The purpose of anting centers on the defensive chemicals secreted by certain ant species, primarily formic acid. Ants from the Formicinae subfamily are often chosen because they spray this pungent compound as an immediate threat response. When the crow presses the ant to its feathers or disturbs a colony, the insect releases the acid, which is distributed into the bird’s plumage.
Ectoparasite Deterrence
One leading explanation is ectoparasite deterrence, suggesting formic acid acts as a natural insecticide and fungicide. The chemical is known to inhibit the growth of microorganisms and may help kill or repel feather mites, lice, and other pests that infest the crow’s feathers and skin. Essentially, the crow is giving itself a chemical bath to maintain feather hygiene and reduce its parasite load.
Feather Maintenance
Another hypothesis suggests anting is related to feather maintenance, particularly during the annual molting period. Molting can cause skin irritation as new feathers emerge, and the acid may help soothe the discomfort. It is also proposed that the chemical secretions may help remove excess preen oil or soften the keratin sheaths surrounding new feathers, making them easier to groom. The behavior is an evolved form of self-care, allowing the crow to harness the ants’ potent chemistry for its own biological benefit.