Ducks are very intelligent. This is almost a King Solomon's story.
Way back in the 50's in Pulau Kerto, my mother reared quite a big brood of ducks and so did her competitive kind of neighbour. Ours was a bigger brood and grew fast because my mum fed them with chopped vegetables and rice husk (grandpa had a rice mill)
One day our neighbour came over to claim a brood of new ducklings, saying that they were hers.Mum was a bit flustered but my cousin (my baby sitter) was quick to the defense. She said that the two ladies should call the mother duck and whoever could call the mother duck home, the brood would belong to her. Our neighbour started to call " Dee, dee, dee...." (Foochow style, not quack, quack)..the mother duck did not make a move. Mum just said, " Dee, dee, dee, and deee.." six times only and the mother duck graceful came towards her with all the ducklings.