This Is Why Songbirds Cover Themselves in Ants

Sam Westreich, PhD

Itching? Parasites? Food preparation?
Cardinals are more photogenic when not covered in insects.Photo by Joshua J. Cotten on Unsplash

No creature in nature exists in a vacuum. We humans like to believe that we are the masters of making use of nature, including other creatures, for our own benefit, but it’s not the case.

There are many symbiotic interactions between different animals. Birds eat the ticks off of rhinos and wildebeest. Clownfish live in the shelter of sea anemones, and drop bits of their meals for the anemone to eat. Honeybees drink the nectar from flowers, and carry the pollen from flower to flower as they do so.

But do you know about the interaction between songbirds and ants?

It’s a behavior called anting, and it’s been observed in more than 200 species of birds — mainly songbirds. The bird either actively places ants onto its body, or passively crouches on an anthill and encourages the ants to crawl over its body.

But what’s the benefit? What do the ants do for the birds?

Unfortunately, like many situations in nature, we don’t know for certain, but we have several hypotheses. Let’s learn what these ants may offer the birds that put them to some sort of use!

Nothing scratches an itch like an ant

Whatever the reason for the ants, most hypotheses suspect it has something to do with their ability to secrete formic acid. This strong acid, with a pH between 2–3, is secreted by ants as a defense against predators; they’ll spray it from their abdomens when threatened, up to a meter away. It kills bacteria and repels predators, as it causes irritation and burning sensations when it lands on exposed skin or the eyes/nose/mouth.

(In comparison, Red Bull has a pH of about 3.3, Pepsi has a pH of about 2.5, and battery acid has a pH of about 1.0.)

One theory of why birds put ants on their bodies is that they want the ants to secrete that formic acid. It’s been observed that birds do this anting behavior most commonly in late summer and early fall, when the birds are molting — they get a rush of new feathers growing in, often to change their appearance to better blend in with their surroundings as the seasons change.

Having feathers grow in is likely an itchy prospect. The formic acid may help to soothe the irritated skin, scratching their itches.

Cleansing with an acid bath

As mentioned, these ants will secrete formic acid when disturbed, as a defense mechanism. Another hypothesis suggests that birds may seek out this acid — not to irritate themselves, but to irritate parasites or bacteria that may be dwelling on their skin.

Birds get a lot of parasites burrowing under their feathers and causing pain and irritation. These are usually lice or mites (lice are six-legged insects, while mites are eight-legged arachnids, relatives of spiders). The mites will eat keratin, the scaly material that is also on the bird’s skin, beak, and feet. Lice tend to eat shed skin bits and feather debris. Both are frustrating for the host.

Formic acid is an insecticide, and has been shown to kill mites (it’s often used to help kill parasitic mites that invade bee colonies). Birds may engage in anting behavior to cleanse themselves of parasites.

In support of this idea, birds have also been found anting with other compounds that act as pesticides, including marigold flowers, mothballs, citrus skins, and even cigarette butts!

Gonna eat some tasty Dixie ants

Our third hypothesis is a bit less kind to the ants. Birds often eat ants; they’re a great protein source. If you’re considering giving up meat for environmental reasons, switching to insect meal is friendlier than other farming methods but doesn’t sacrifice protein content.

Of course, birds don’t want to eat an ant that’s full of formic acid. Nasty, burny stuff. Anting may be a learned method by which the bird can induce ants to empty out their store of formic acid, leaving the ant as a tasty, de-venomed snack.

Some experiments validate this hypothesis. One, looking at how hand-raised blue jays acted when presented with ants, showed that the anting behavior is present even in blue jays that had never seen ants before in their life.

More interesting: if the ants had no formic acid, the blue jays simply gulped them down. If the ants did have acid, on the other hand, they were rubbed on the bird first to discharge their acid, and then eaten afterward.

One challenge for birds is that the formic acid is stored right next to an ant’s crop, a pouch that stores food before digestion and is a big portion of the ant’s overall nutritional value as a food source. How do you empty out the acid, without removing the nutritious crop?

Anting may be the answer.

We still don’t know for certain

Like many scientific questions, we have several strong hypotheses, each with supporting data. Which one is the most correct, however? Sadly, we might never know for certain, or it may turn out that multiple hypotheses are simultaneously correct (or one may be correct for some bird species but different for others).

The most likely answer is that birds perform anting to take advantage of all these benefits. Scratch an itch, clean off nasty parasites — and maybe, as an added bonus, get a tasty meal in the process!

Anting is an interesting interaction between different species in nature. It’s probably not true symbiosis, as the ants don’t seem to get anything out of it; they’re wasting their acid trying to defend against an inferred predator. It is more likely a commensal relationship, where one party receives a benefit (the bird) and the other doesn’t really get anything (the ant).

We like to claim that humans are the only tool users, but how many of us have considered using ants to clean ourselves of parasites? Perhaps we need to consider that we are less distinct from other creatures than we want to believe.

Can you think of other examples of commensal relationships, where one side gains a benefit and the other side remains neutral?


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A microbiome scientist working at a tech startup in Silicon Valley, Sam Westreich provides insights into science and technology, exploring the strangest areas of biology, science, and biotechnology.

Mountain View, CA

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