I believe they're ground foragers.

They're specifically ground foragers, eating whatever they can find, ranging from seeds from dried out plants, fallen fruit (depending on whatever may grow, where they are), and low-growing plants like grass.

Though being a part of the cockatoo family, I would especially expect them to want to get into anything they find, so throwing the markers on the floor could just be the natural playing behavior of their inner 2-year-old.

They're ground feeders in the wild, primarily grass seed.