Dr. Bird Whistle appeared in an episode of Bert and Ernie's Great Adventures

Dr. Bird Whistle uses bird calls to capture rare birds for his collection. He goes to Guatemala to capture the native bird, the quetzal. Secret Agents 00-Bert and 00-Ernie (along with Bernice) go follow Dr. Bird Whistle into the Guatemalan jungle and attempt to capture the doctor. However Bernice ends up caught in a cage, and Bird Whistle releases her, finding pigeons common. He finds the quetzal and chase it, while Bert discovers Bernice is gone. They set another trap for him, which accidentally traps the quetzal, while another trap gets Bird Whistle. Now seeing how the birds feel, he promises to release the birds. Agent Bernice appears and reveals she set the trap.