The term 'relative of the extinct moa' can be answered by the 4-letter word 'KIWI'. The KIWI is a species of flightless bird native to New Zealand. It is the only living species of its genus, Apteryx, and is the smallest living ratite. The KIWI is a national symbol of New Zealand and is considered an endangered species due to habitat loss and predation by introduced species. The KIWI is related to the extinct moa, which was a large, flightless bird that lived in New Zealand until the 1500s.