Fossil avian assemblage of pitfall origin from Holocene sediments in Amphitheatre Cave (G-2), south-western Victoria, Australia

The fossil avian assemblage from Amphitheatre Cave (6 km north of the township of Nelson, Victoria, Australia) consists of 27 species of birds. Three dominate the assemblage with 63% of the total minimum number of individuals (i.e., Gallinula mortierii, Dasyornis broadbenti and Dasyornis brachypterus). Most of the material originated from a pitfall accumulation, based upon the large percentage of individuals belonging to terrestrial species with elements lacking the damage characteristic of vertebrate accumulators. Geographic range extensions are noted for three species (i.e., Gallinula mortierii, D. brachypterus and Ptilonorhynchus violaceus). Assuming the assemblage is intra-contemporaneous, the reconstruction of vegetation at the time of deposition would include; wetlands with some areas of short cropped grass, bordered by wet heathland, which subsequently gave way to Eucalyptus open forest formation away from the water source and Eucalyptus tall open forest formation in the gullies. The age of the deposit (4,670 ± 90 y.B.P.: NZA 700) is based upon a single radiocarbon date on bone. BAIRD, R.F. , 1992. Fossil avian assemblage of pitfall ongm from Holocene sediments in Amphitheatre Cave (G-2), south-western Victoria, Australia. Records of the Australian Museum 44(1): 21-44. 21 Amphitheatre Cave (G-2: Matthews, 1985) is located approximately 6 km north of the township of Nelson, south-western Victoria (38°03'S 141°01'E) and occurs in the central part of an easterly facing cliff, approximately 15 m above the Glenelg River. of the fossil material, F.S. Colliver (i.e., Colliver's Cave: The exact location of the cave from which this material came, was unknown for a number of years, and it was therefore referred to by the name of the collector Rich & Baird, 1986; Baird, 1986). Recently a foray was organised, through the help of the Department of Conservation Forests and Lands, where the author was able to view cave entrances from the river. At this time the cave was confirmed as being the southern entrance of Amphitheatre Cave (G-2), matching a photo of the cave entrance provided in Colliver's (1938) article on 22 Records of the Australian Museum (1992) Vol.44 the deposit (see Fig.1). Note that the entrance to the cave is actually below that indicated by Colliver, and that the area he indicated is only shadow produced by a small overhang. "Cave has three entrances to high bifurcating joint controlled passage 80 m long, 18 m deep. Main chamber has large aven. Two entrances are joint enlargements in cliff face 15 m above river level, third entrance is enlarged solution tube 30 m deep x 1.5 m diameter. " (Davey & White, 1986). See Figure 2 for a plan view and position of excavation within the cave. The excavation was started by F.S. Colliver on April 20 and 21, 1935 (Easter weekend), and completed over three subsequent trips (Colliver, 1938). The material was collected by bringing " . handfuls of the flour [sediment within the cave] at a time and spread it on the surface within a daylight area, and picked out any small bones, jaws or individual teeth that appeared. The bigger bones were felt within the flour and gently eased out" (Colliver, personal communication). The cave occurs on the Follett C\Jastal Plain (Land Conservation Council, 1981) of south-western Victoria. This region is characterised by a dissected coastal plain with a variation in elevation between o to 60 m. Subparallel consolidated limestone ridges trend north-west to west-north-west, with inter-dune corridors between 2 to 11 km wide. These are thought to mark former Pleistocene shorelines. Sandsheets of orange siliceous sand are widespread. The local climate consists of rainfall with a winter maximum of 112 mm and a summer minimum of 28 mm (average rainfall) and temperature ranges from 3.6 to 13.7°C (range of mean monthly temperatures) in June to 10.8 to 25.2°C in January, based upon the rainfall and temperature curves of the nearest weather station in Rennick, Victoria (approximately 19.5 km north of Amphitheatre Cave). Westerly winds predominate. The local vegetation consists largely of woodland or open forest, composed of brown stringy bark (Eucalyptus baxteri), messmate (E. obliqua), manna gum (E. viminalis), shining peppermint (E. nitida) and swamp gum (E. ovata), with extensive heaths as understorey. In the immediate vicinity of the cave the vegetation is a mixture of open scrub, heathland and open forest (Land Conservation Council, 1981). For a history of vegetation changes in the area refer to Baird (1985). Material and Methods The material reported on herein was gleaned from several drawers of material in the Museum of Victoria, Department of Vertebrate Fossils, labelled as collected by F.S. Colliver from Amphitheatre Cave, Glenelg River region (see Introduction). To the best of my knowledge all of the avian material available has been studied, though for some taxa, only higher taxonomic level determinations are presented. Modem comparative material used in the identifications was provided by the Department of Ornithology, Museum of Victoria and Department of Ornithology, South Australian Museum. All of the fossil material discussed will be deposited in the Museum of Victoria, Department of Vertebrate Fossils. Museum of Victoria catalogue numbers can be found in the Materials section of each species account. A prefix 'P' should accompany each number but has been omitted for conservation of space. The Scientific names used in each account follow Condon (1975) and Schodde (1975). Taxa previously unknown from sub-fossil and fossil deposits are noted (unpublished records in the faunal lists of Rich & van Tets (1982) are not considered formally confirmed Fig.I. Photographs of the entrance to Amphitheatre Cave, including the original from Colliver (19J8-) and a more recent one taken by the author. Note that in the original photo the arrow only points to a small overhang, in the new photo both the south and the north entrances can be discerned. The south entrance is 15 m above the water level. records as no full diagnoses are provided). Minimum numbers of individuals were determined by the standard method of counting the most abundant element from a particular side. Geographical ranges for each species are here assumed to be the same as the current range, unless otherwise noted. The current range of each species is assumed to include the area surrounding the amphitheatre section of the Glenelg River, unless mentioned otherwise. Anatomical terminology follows Baumel et al. (1979). All measurements in the text are in millimetres. Standard measurements in the text are indicated in brackets and follow the guidelines in von den Driesch (1976) unless stated otherwise. All measurements were taken with vernier callipers accurate to 0.05 mm and were rounded to the nearest 0.1 mm. Species determination is based upon mensural criteria in every species account except where otherwise stated. Botanical nomenclature follows the guidelines of Specht (1981). All tables referred to throughout the paper are included in Appendix I. Abbreviations used in the text, figures and appendices are listed in Appendix 11. Material identified as juvenile is based upon the criteria of having a " . pitted appearance of the surface of the bone and incomplete ossification of the articular o Baird: Fossil avian assemblage 23 facets . " (Campbell, 1979: 17). Morphological characters for determinations higher than species level are included in Appendix Ill, unless only one element is considered, in which case they are included in each species account. Characteristics include those separating the species from closest relatives and other families which may have similar appearance to the elements in question. This is not supposed to be an exhaustive account of characters separating the species, families and orders in question but only a guide to the characters used to identify the elements in question from all other Australian taxa with similar appearance. All bird species currently recorded from the Australian continent and Tasmania were included in the comparisons unless noted otherwise (in the Characters section of the species accounts). Unless otherwise stated, actualism or methodological uniformitarianism is assumed to be valid (see Simpson, 1970 and Gould, 1965, 1985, respectively). This implies that if a species is restricted to a particular set of environmental parameters currently, the species was also restricted to those parameters in the past. Although there are several examples of modern species, now restricted to specific habitats, that are found in deposits whose faunal composition suggests that those species inhabited a wider range of habitats in the past than is presently displayed, I have not presumed wider ecological tolerances for species unless the fauna, as a whole, or