Maeve beat me to the no poison in the environment is good poison. Secondary poisoning (owl eats a poisoned rodent) is one of the biggest killers of owls here in Maine.

On a happier note: All viewable and established osprey nests at the park are inhabited by their previous residents. The Eastern Phoebes are back, and I heard my first hermit thrush of the season yesterday. Other recent arrivals are the yellow-shafted flickers and a ruby-crowned kinglet.