Sixteen species of birds have been identified from Quaternary-aged deposits in "Green Waterhole Cave" (L-81 of the Cave Exploration Group of South Australia cave classification) approximately twenty-four kilometres west of Mt Gambier, south-eastern South Australia. All but three species are referable to modern species. The exceptions are a new accipitrid (to be described by Drs P.V. Rich and G.F. van Tets), a new species of coucal, and a new species of passeriform. It is suggested that one of the extant species and all of the new taxa are examples of Pleistocene gigantism. Geographic range extensions are demonstrated for Gallinula mortierii, Calyptorhynchus lathami and the genera Centropus and Orthonyx. Taphonomic study of the deposit, using faunal composition as the main indicator, implies that water was the accumulating agent. Relative dating of the locality has been made by using sea level curves (last sea level transgression over the present eustatic high) and the presence of megafauna. Dating of the last sea level transgression suggests a maximum age of 125,000 years before present (y.B.P.) for the opening of the cave to the surface, because the cave lacks marine influence. The maximum age of accumulation is anytime before 15,000 y.B.P., which is the time of last occurrence of most mammalian megafauna.