Sam, tho I've heard cuckoos (they have a distinctive call), I don't think there's enough of them to control a pest very much. Supposedly they are one of the few to eat gypsy moth cats, but I don't think they ever had a significant effect.

Now if starlings ate them.......

Hardly a living box left round here. It's a killer, not just unsightly. I lost all my topiaries grown from cuttings over the years. Box is native here and I fear for the wild population.

Personally I've not seen any alternative which clips so well for a formal shape. I've tried Ilex crenata and it just isn't the same.

Box_tree_caterpillar_Factsheet_2024.pdf https://share.google/qLA9axjFVsFlAEmHT 

Just saw a moth in the garden this afternoon. I don't have any box left for it to attack.

One frequent complaint about boxwood is the smell of cat pee. Wonder what those caterpillars taste like? What respectable bird would want to eat them? I tried cross posting this on the birdwatchers forum, can't find it.

It's here: https://www.gardenweb.com/discussions/bird