I looked carefully at my photos and saw that they have distinct bill markings, one with a very small mark close to the nail, the other with a larger U shape mark. The older bird, with the U shape mark (I'll call her Stripe) appears to the the East Park resident. The younger bird, still with tiny body feathers has a small bill patch and matches the bill marks - and tiny white feathers around its bill - of the one that was at Pearson Park. Despite being younger, this bird was bigger and has a larger head, with a Roman profile and a thicker neck and a heavier head, so it might be well a male. Since last saw both birds I was impressed how much more grown up they look. Their neck stripes are better delineated, their head shapes less gentle, and they have a more silvery backs as they have moulted their juvenile feathers. The Pinkfeet stayed near each other in the flock, but one lunged at the other when it got too close. At some point the flock got wary of a radio controlled car, and after a crescendo of cackles, they flew off.
'Dot' Pearson Park 20/11/2014
East Park, today. A male?
'Stripe' East Park 14/2/2014
East Park, today, a female?
Dot's juvenile feathers very noticeable in the flanks, with some adult feathers, darker and silvery just over his legs.
Stripe seems to have a full adult plumage now.