When my mother and I moved in to our new home, a pair of pigeons decided to take refuge in a small area of elevated roofing. We got rid of them by using moth balls. Now you can't just throw a handful in their nest because the clever birds will just toss them out. So what we did was take an old plastic butter container, puncture the sides and lid with an ice pick. Then filled it with moth balls and duct tape it where the birds usually hang out. The nesting pair left in two days, but tried again the fallowing year so we had to do the procedure over again. We have lived in the house for 27 years and never had a roosting problem again.