If a crow is indeed the culprit, kill one crow and leave it in the yard. The others will not be back. Crows are extremely intelligent. When we moved here (50 years ago), the crows would knock the lids off of the garbage cans and rip open the garbage bags. One night I wired a padded jump trap to the can and set it on top of the garbage. The next morning all Hades broke out in the back yard. The Princess said, "What is going on?" My reply, "Crow education". I went outside and all but the trapped crow left. The trapped crow flattened out and played dead. After a bit of a talk I released the crow. 50 years later and the crows go nowhere near my garbage.