The term 'Bygone Birds' refers to four extinct species of birds: DODOS (5 letters), Moas (4 letters), SSTs (4 letters), and Dodoes (6 letters). The Dodo was a large, flightless bird native to the island of Mauritius in the Indian Ocean. The Moa was a giant, flightless bird that lived in New Zealand until the 1400s. SSTs were supersonic transport planes developed by the British and French in the 1960s. Finally, Dodoes were a species of flightless birds that lived in the Caribbean until the 1600s.