I believe she tells them to cover their ears with wax. The Sirens were known to enhcant sailors with their music and songs and lure them to their deaths. To prevent that Circe had them plug their ears so they wouldn't be enchanted, and go to their death.
They Moved because there was Fertile Land and better soil, Job Oppurtunities and Housing. There also moved for Freedom and Safety.
-Hope this Helps
They got free land that's your answer
