Possible Clues:

• Bygone flightless bird
• Perform at the double thus no more
• Repeated encouragement from reactionary person
• Bird extinct since the late 17th century
• Odd about duck being an extinct species
• Bird extinct since the late 1600s
• Dunce
• Not the smartest extinct bird
• Two parties that never got off the ground?
• Bygone bird of Mauritius