The Cape Barren goose ( Cereopsis novaehollandiae ) is a species of goose endemic to southern Australia . It was first formally described by the English ornithologist John Latham in 1801. Adult Cape Barren geese are large birds, typically measuring 75 to 100 centimetres (30 to 39 inches) long and weighing between 3.7 to 5.2 kilograms (8.2 to 11.5 pounds), with males generally being larger than females. The plumage is mostly pale grey with a slight brown tint. The head is somewhat small in proportion to the body and mostly grey in colour, save for a pale whitish patch on the forehead and crown. Cape Barren geese are largely terrestrial , only occasionally swimming. They predominantly graze on grasses, sedges , legumes , herbs , and succulents . This group of Cape Barren geese in flight was photographed near Hanson Bay, on Kangaroo Island in South Australia .