There are two ducks on the pond for the cleanup hitter.
A coded warning called out by men working in a shearing shed alerting each other that guests ("ducks") are present ("in the pond"), so that for politeness they can moderate their language, ie, avoid obscenities or subjects improper for mixed company
Usually the wool presser calls first, because most visitors to a shed come through the wool room. 'Ducks on the Pond!' he calls, and the warning is taken up again down along the shearing board.