Can my bird find me behind the wall? 

Training a bird for recall is relatively easy but there are different levels of that.
For example, recall inside a room, from a short distance and inside the bision of the bird is the dirst step... but doing so outside and behind an obstacle is way more difficult.
Can my bird find me behind the wall of my house? She'd be good at hide and seek!
My trained cockatiels free fly every day it's possible, they are hand reared and trained since very young chicks.
Cockatiel training is vital as well as gaining your cockatiel trust.
Never try to cockatiel free flight or any other parrot without prior intensive training, not just recall indoor.