Blue Duck is famous for two reasons—Larry McMurtry had a character by that name in Lonesome Dove, and the real man was photographed with Belle Starr.
Duck shot and killed a man in the Indian Territory in 1884; he was sentenced to death by Hanging Judge Isaac Parker in July 1886. That was later commuted to life in prison. Supposedly, his lawyer had that Belle Starr photo taken to get publicity for the case (it must have worked). It’s unclear if Duck was otherwise involved with Belle. He died of TB in 1895.