Possible Clues:

• French novelist Robert ___, upon whose work the 1973 thriller 'The Day of the Dolphin' is based
• He sang about Bo and Luke
• Haggard of country /music
• Haggard who sang 'Okie From Muskogee'
• First name among country crooners
• Country music's Haggard
• It's a mere matter of about fifty to make the bird black
• Oberon's name for a bird
• To get me around Schubert's king is enough to make the bird black
• European thrush