Australian magpie. This bird is not fully mature, the giveaway being the grey in the feathers on his/her back (both sexes look much the same). When fully mature those feathers will be white.
Magpies have a range of vocalizations ranging from argumentative squawks to beautiful warbling songs. They can learn to talk too. A couple of anecdotes from my father's childhood concern a talking magpie. My father's father was a minister, and once when he was preaching, the magpie strolled down the aisle calling 'Who threw that ball? Who?' It also liked to call out, 'Alvin, put down that axe', mimicking my father's mother.
In spring, some breeding males get aggressive and swoop people, and can cause severe injury if they connect, but most are not a problem.