The flight feathers are simply cut off painlessly. It's just like cutting hair, it's all dead and it's totally painless. They grow back continuously, just like hair. I had a goffins cockatoo (the closes thing I have ever had to a human baby, she was an angel) and she'd lift out her beautiful, warm wing and hold it out for me so I cut her flight feathers. Most birds will fly away if given the chance, so it's a wise thing to do to a bird that has playtime outside of it's cage.

People should not clip a canary's feathers, or a finch, or any other bird that's not a parrot. They can't adapt to the loss of their flight.