I am from Qld and therefore can readily identify a Silver Gull.
At Cheyne Beach, WA in mid-March I got pics of Pacific Gull - 2 adults and 2 2nd year birds that seemed to be a family group.
There was another Gull (pic 3) that was not associating with the 4 above - is it also a 1st year Pacific Gull?
I'm sure it is Peter.
M-L
I can't help with age, but the massive bill is a good id feature for Pacific Gulls.