They like to stay in coops this time of year since there's food available in there. Poison would probably be the most effective thing to use in this case, because as oldhenlikesdogs said, if you're seeing them, you have a lot of them. They reproduce like crazy. I'd patch up any rat holes you can see on the coop with something they can't chew through, and remove any rat nests you can find. I found a rat nest in the roof of my coop just the other week. I used sheet metal on my coop for the rat holes. As for poison, this sounds safer for other animals:
X2! Make sure your ducks don't get near the poison--or the traps. They aren't as dumb as some chickens but some people I know ended up with some baaaad cases.