The term 'Bird of Mauritius, Extinct' is referring to the DODO, a flightless bird that was native to the island of Mauritius in the Indian Ocean. The DODO became extinct in the late 17th century due to human activity and the introduction of non-native species. It was a large, flightless bird with a long beak and short wings, and it was unable to fly due to its size and lack of natural predators on the island.