A survey of diurnal birds of the Royal Botanic Gardens Cranbourne (RBGC), Victoria was undertaken during most months between January 1999 and December 2004. Bird species were recorded at ten, two-hectare areas representing the major habitat types available. Incidental observations of other species were also recorded generally throughout the site. The results of the study suggest that the majority of species known from the extensive Gippsland Plains Bioregion still occur at the RBGC. A rich avifauna comprising 160 species was recorded during the study and it included a range of taxa now rare or threatened elsewhere in the region. Temporal and spatial patterns in the reporting rates of species are examined, including a comparison with a similar survey conducted at the site between 1989 and 1992. While many birds were widespread across the RBGC and present throughout the year, there were clear differences in the avifauna recorded at different sites and seasons and there was evidence of significant long-term trends in some species. The RBGC is one of the few remaining moderately sized patches of lowland vegetation in the Port Phillip-Westernport Region and is identified as an important site for the conservation of biodiversity. The performance of this and other similar sized patches of remnant vegetation in providing habitat for native birds may be crucial to the conservation of bird diversity in the region.