DemographicsBirnam (Toowoomba - Qld) is approximately 3.97 square kilometres. In 2016 the population of Birnam (Toowoomba - Qld) was 65. The population is 47% male and 53% female. On average the monthly mortgage repayments in Birnam (Toowoomba - Qld) are $0 to $299. The most common weekly income bracket is $800 to $999 per week. Weekly rents in the area are on average $0 to $74.