> This theory posits that the formic acid produced by ants might act as a sort of stimulant for birds, and might even be addictive.

I like that idea. I also remember growing up we used to put straw on top of ant hills waiting for ants to "attack it" with formic acid, then we'd lick the straw. It was a fun sour taste. Since birds groom their feathers, maybe they just enjoy it like kids might enjoy sour candy.

Where did you learn to do that?

Other kids showed me. How did they learn? Not sure, same way :-) But yeah, at some point someone decided "Hey, I know, I'll put this stick in the anthill then lick it to see what it tastes like".

Yes that's me. I am enjoying my exciting new life as a carnival performer on HN

Though it is hard to type with three missing fingers...

My dog used to rub himself on earthworms he found in the lawn. Very strange. I thought maybe since earthworms have high antifungal and and antibacterial properties, he was trying to medicate himself? Ants have similar properties.

Interesting. Was it just earth worms? Many breeds rub their bodies into the earth especially when there's a strong (usually bad) odor present.

I've heard the theory that the behavior is intended to mask the dog's own odor which could aid in hunting.

Come to think of it, he did rub on other things too like that. Maybe it was to hide his scent.