Parrots talking? hole opening in and out? :S

Question

i work in a vets and we have a number of parrots there, today when i was cleaning out one of their cages i was looking at one of the parrots and i realized that whenever he spoke from his mouth, at the bottom of his body there is a hole (it looked like a bum hole on a human, without sounding completely crude, im trying to explain) and it seemed to like expand itself whenever the parrot made a noise, and then go back to normal after?

im so confused as to what it is

is this their voice box.. which somehow is at the bottom of their body?

Answer 1

If you watch dogs bark their a**s does the exact same thing.

Answer 2

it's the cloaca.

which is basically an all purpose hole.

Used for reproduction, urine, f***s, etc.