Ardea novaehollandiae ( White faced Heron)

These whiate-faced herons are self-introduced to NZ and started breeding here in around the 1940's.  They fly with a slow/steady wing- beat. Laying 3-5 eggs both cock and hen incubating for around 26 days.
 My data source tells me they are abundant but this year I have noticed a lot less than previous years around the Christchurch Estuary. Not sure why. 
Cold wet SW in ChCh today -
rgds Poo