This bird, often called a crow, is very common along Campbells Creek. It may be that the the food resources available at the Castlemaine Landfill (rubbish tip) are increasing its numbers above what the landscape could normally support.
Read more about and see more of this bird at the Wikipedia web site.
Hear, read about and see more of this bird at the Birds in Backyards web site.
Hear this bird at the Xeno-Canto web site.
Or find even more information about this bird at the Google web site.