My Screech Owl Companion co-author Scott Weston writes:

I work in Salem, Mass.,  and the post office where the screech owl was found poisoned is about 800 feet from where the Peabody Essex Museum put up one of my screech owl nest boxes -- such a hindrance for success.

https://patch.com/massachusetts/swampscott/s/j4to7/salem-owls-survival-fight-spurs-push-for-action-against-rodentcides

The good news is the Massachusetts Legislature is considering legislation to ban the worst of these rat poisons.