Atlas of Living Australia (ALA) via https://bie.ala.org.au/species/

White-necked Heron

Ardea pacifica

The white-necked heron or Pacific heron (Ardea pacifica) is a species of heron that is found on most of the Australian continent wherever freshwater habitats exist. It is also found in parts of Indonesia and New Guinea, but is uncommon in Tasmania. The populations of this species in Australia are known to be nomadic like most water birds in Australia, moving from one water source to another, often entering habitats they have not previously occupied, taking advantage of flooding and heavy rain where the surplus of food allows them to breed and raise their young. Irruptive movements may occur when environmental conditions are right in places where the species has been rare or absent.