Well, now we have to define 'answer questions.' The birds aren't answering questions like humans do in conversations, although there are some parrots who, after a lifetime of training, seem to be able to give basic contextually correct answers, like gorillas who were taught sign language.
The birds with mimicry abilities learn to mimic all sorts of things, especially other bird and animal noises. If they're around humans, they mimic humans' speech, songs, and music. They're just being prompted with a reward to vocalize something they've heard. Just like the other birds are prompted to fly from here to there.
I suppose it would have been better for a show that presents the birds' natural behaviors to have a mimic show-off mimicking other birds.
This is different from say, training a bird to peck at certain keys on a musical keyboard to play at song. That would be an unnatural trick. But mimicking humans and anything else in their environment is a natural ability of mimic birds.
The payoff is at 1:45 to the end...
