Crows are considered migratory birds and there are federal regulations governing their seasons. They can be called with blown calls but you can get tired after a few hours. I have an electronic caller and several self blown calls that I use. They are a lot like geese in that the warmer winters we have had in the past have encouraged them not to migrate so far south and so it seems like they don't migrate at all...but many still do.
Good luck and have fun.