While Australia's endemic
Pacific gull is the most common large gull seen around Southern Victoria I read that the Kelp gull
Larus dominicanus has been moving in on its territory since the 1940s. Kelp gulls breed on many Southern Hemisphere coasts. In Australia they compete with Pacific gull as they share similar habitat, diet and behaviours (including dropping molluscs from a height to smash them).
It was a long time before I started to recognise that not all the large gulls I was seeing were Pacific gulls. I have since become aware that a particular rock stack at
The Nobbies on Phillip Island is a popular site for Kelp gull which actually breed there.