Just as it states, this behavior entails a parrot sticking out its tongue, often to the side, and waving it about.
Macaws are especially prone to this silly tongue action, and it appears to be a play behavior. When a human responds with tongue wiggling of his/her own, macaws often flash their eyes happily and wag their tongues with even more enthusiasm.
Tongue wiggling can also be seen when a bird is gingerly testing a new surface, though it usually touches with its beak first, and then the tongue. The nerves in the beak and especially the tongue are quite sensitive to texture and temperature.
Nothing, except to join in the play!
Disclaimer: BirdChannel.com’s Bird Behavior Index is intended for educational purposes only. It is not meant to replace the expertise and experience of a professional veterinarian. Do not use the information presented here to make decisions about your bird’s health if you suspect your pet is sick. If your pet is showing signs of illness or you notice changes in your bird’s behavior, take your pet to the nearest veterinarian or an emergency pet clinic as soon as possible.