It is not good to use poison bait due to the scavengers like hawks, foxes, buzzards, etc that clean up the environment of dead animals if it is not under your full control.
A Havahart trap is the way to go and then just drown the varmint or shoot it if it is legal in your area. You can find all sizes of Havahart traps at the Tractor Store. Now is the time to trap them before they have babies.
I use the small Havahart trap for mice in the shed and then feed them to the fox. Squirrels are put on the top of a fence post that have been drowned and the hawk finds them.
I have foxes that kill mice to prevent Lyme disease and hawks that keep down the squirrel population at one place: