Mockingbirds don't do one thing but make music for us to enjoy. They don't eat up people's gardens, don't nest in corncribs, they don't do one thing but sing their hearts out for us. That's why it's a sin to kill a mockingbird.
No, they are not but they don't stick around for winter. When you start to hear them sing in the morning after a couple months of silence in the morning its a welcome sound to me.