When they know what the click means, you can capture the behaviour as the bird stretches his wings, which means - while he doing it you click and then treat...
A lot of behaviours can be taught this way...
Once the bird knows that it gets a c/t for a behaviour, it'll start offering different behaviours, if the ones already taught don't pay off... of course if you ask for a specific behaviour you need to c/t..
An example: Put a box on the table. and let the bird play with it - you might see many behaviours, you'd like to capture, such as wings out, getting into the box, throwing things out of the box etc. etc.
When the bird really knows clicker training, the possibilities are endless...
ETA: I use a cue "wings" as well as a visual cue by holding out my arms...