Birt was a rover and, after being recruited to Essendon from Ballarat, he made his VFL debut in 1957. The following year he had one of his finest seasons, finishing 6th in the Brownlow Medal and topping Essendon's goalkicking list with 31 goals. He was a premiership player in 1962 and 1965, as well as playing in two losing Grand Finals, and won the
W. S. Crichton Medal for his club's Best and Fairest in 1961, 1965 and 1967.
Birt was playing coach for West Torrens in the SANFL from 1968 to 1970.
Victoria (VFL) 26.24 (180) defeated Tasmania 11.13 (79), at North Hobart Oval, 9 June 1966, crowd: 20,047 Victoria (VFL) 16.23 (119) defeated South Australia 7.9 (51), at North Hobart Oval, 11 June 1966, crowd: 23,764 Victoria (VFL) 14.17 (101) defeated Victoria (VFA) 9.7 (61), at North Hobart Oval, 13 June 1966, crowd: 13,969 Victoria (VFL) 15.10 (100) defeated Western Australia 13.7 (85), at North Hobart Oval, 18 June 1966, crowd: 23,368