In 1912, the Australian ornithologist Gregory M. Mathews recognised three living subspecies of emu,[25] D. n. novaehollandiae (Latham, 1790),[26] D. n. woodwardi Mathews, 1912 [27] and D. n. rothschildi Mathews, 1912.[28] However, the Handbook of the Birds of the World argues that the last two of these subspecies are invalid; natural variations in plumage colour and the nomadic nature of the species make it likely that there is a single race in mainland Australia.[5][30] Examination of the DNA of the King Island emu shows this bird to be closely related to the mainland emu and hence best treated as a subspecies.[7]