 He first joined the CSIRO Division of Plant Industry but later transferred to the Division of Wildlife and carried out extensive research on malleefowl, waterfowl, especially magpie geese, and pigeons.He eventually became Chief of the Division and was instrumental in proposals that led to the establishment of Kakadu National Park.Harrold Frith was a member of the Royal Australasian Ornithologists Union (RAOU), and prominent among those pressing for reform of the organisation in the late 1960s.