We've read a bit more on Acrobat ants, and it seems that they are quite compatible with Owls. According to Fred Gehlbach, the world authority on Eastern Screech Owls (he wrote the book on them), Acrobat ants often do live in Eastern Screech Owl nests, and can deter predators. It is a tradeoff, however, as they will eat any cached food.
Acrobat ants, though, live in occupied boxes and cavities. Their brood (larvae, pupae) is housed in damp nest debris...They sting and spray me but not the owls and bite pieces out of food caches, removing these to their brood, often out of reach of the owls...Such symbiont competition could be severe, if Texas blind snakes did not reduce the numbers of at least some insect competitors, and my limited observations suggest they do....Texas blind snakes are an earthworm-sized snake that is prey for the owls, but as they are slippery, they sometimes get away in the nest box. In this case, they often set up residence in the nesting material, out of reach of the owls, and feed off insects and larvae in the nesting material.
But there is a possible tradeoff in the owl-snake-ant symbiotic "triangle." Although the snakes are beneficial in removing ant brood, acrobat ants may protect the owls by attacking potential predators. If ants are indeed displaced by blind snake predation on their brood, the protection disappears. Which is mor important, reducing or eliminating and competition for cached food or cohabitation by the ants and hence their protection? Right now I cannot say, but I have noticed that flammulated and western screech owls are also apparently protected by cavity-cohabiting ants that do not disturb their owlets.In our nest box, we have observed relatively little cached food during the season. About 3 times per season, something big, like a rodent or bird, will remain in the box for about a day while it is consumed, but most of the rest of the food is consumed within minutes after it is brought in, so the ants would have no effect on it. In Gehlbach's book, I have read accounts of significant food caches of perhaps even more than 1 bird or rat at a time. Our owls seem to subsist mostly on geckos, lizards, cockroaches, and other insects.