The rat-poison problem is gaining attention across the U.S. and Canada. (British Columbia has banned the nastiest ones, the so-called "second generation" anticoagulant rodenticides.
Here's a video from Valentine's Day weekend from the International Owl Center in Minnesota by rodenticide and Barn Owl expert Sofi Hindmarch that explains the problem, and what can be done.
(A big thank you to the International Owl Center for creating this video.)
15:00: History of rodenticides
21-23:00: Why these "second generation" anticoagulant rodenticides are so nasty
39:00: How these poisons accumulate in the environment (like lead and DDT)
1:09: What can be done...
1:10: Preventive measures
1:11: Rodenticides should be used as a last resort, and not permanently
1:12: Summing up (See Point 5 below)