Sunny is my yowler. He usually does this at night after I've gotten into bed. I call his name and he usually stops but not always. He also does this during the day to get Storm's or Cirrus's attention because he wants to play. My RB Pepper used to do this too. He'd be walking down the hall and then he'd start yowling like he was in pain. I'd call him and then finally go see what his problem was. He's fine and just wants some attention. Storm used to always run to him when he did this but quickly learned that it meant nothing was wrong.