The term 'OLD BIRD' can be broken down into three crossword solutions: MOA (3 letters), DODO (4 letters), and COOT (4 letters). MOA is an extinct species of large, flightless bird native to New Zealand. The DODO is an extinct species of flightless bird that was endemic to the island of Mauritius in the Indian Ocean. The COOT is a small waterbird that is found in both Eurasia and North America. All three of these birds are considered old birds due to their long history and extinction.