The birds had forgotten what they'd learned. This research has important medical applications. When a mammal has a head injury, it can't regrow new brain cells. If we can learn what makes canary brain cells grow, maybe we can regenerate human cells as well. In the wild, parrots teach each other where to find the most edible fruits and nuts, safe water sources, and mineral-rich soils.
Parrots also signal each other when danger is near.
Interestingly, though, handraised parrots vocalize more than their wild counterparts. Birds, of course, don't have lips, and their tongues aren't flexible in the same way as ours, although parrots do seem to use their beaks and tongues to help articulate words. The larynx of a bird lacks vocal cords. The shape of the syrinx and the sounds it emits are controlled by muscles attached to the bronchi. Sounds are believed to be produced by the air forced through slots in the syringeal membranes.