This study assessed differences in avian biodiversity across different forest age-classes, including mature stands (> 100 years), in a managed, mixed-species eucalypt forest located in Gippsland, south-eastern Australia. Avian surveys and detailed habitat measurements were initially carried out in 50 two hectare stands ranging in age from 100 years. Extensive wildfire which occurred during the study reduced the number of sites to 28 (seven in each of four age classes) upon which analyses and inferences were made. Mature vegetation (> 100 years) had the greatest richness, abundance and biomass of birds. Key ecological resources, such as tree-hollows for nesting, generally occurred mostly in stands > 60 years. There were quantum increases in all measures of avian biodiversity in mature stands (> 100 years). The visualisation of the survey data is part of an interoperable web-GIS maintained by the Centre for eResearch and Digital Innovation (CeRDI) at Federation University Australia (FedUni).