Movement of Cape Barren geese

Hi
Have been contacted by the Environment and Sustainability Officer at HMAS
Cerberus (Vic) who has noted a dramatic drop in their numbers of geese
recently.
I know that numbers also fluctuate quite dramatically at the WTP in
Werribee, so I am wondering if anyone knows where they go to – is it just a
generally nomadic species or do they go to specific breeding sites at some
times of year?
Thanks