Beruldsen in 'A Field Guide to Nests and Eggs of Australian Birds', states: 'No actual nest constructed. Old nests, often those of Fuica or Tribonyx species, hollows in trees, dense bushy vegetation such as lignum or slatburh or stumps, logs and the like are chosen.'
The above is a notable record for the ACT which has very few Pink-eared Duck breeding records. It may, in fact, be the first image of birds in the nest for the ACT.