The term 'Bye-Bye Birdie' is a reference to the 1960 musical comedy film of the same name. The crossword solution for this term is 'DODO, ' which is a flightless bird that is now extinct. The DODO was native to the island of Mauritius in the Indian Ocean and was hunted to extinction by the end of the 17th century. The DODO has become an iconic symbol of extinction, and its name has been used as a metaphor for something that has become extinct or obsolete.