I looked it up and..
Congratulations!! I believe your parrot is CLUCKING!!
here's some videos of it:
yup..you have the best clucking parrot video on youtube
it all makes sense now,e.g. the body movement when the sound is being made(look up "bukk bukk" on youtube if you want to see a chicken do it)
and I'm sure you're gonna ask about the timing/reason so here's a snipit from...someplace( ) written by the owner of a Amazon parrot:
...
During mating season she frequently draws my attention to the open top drawer of the dresser. She sits peering into it and then clucking at me, as if urging me to consider moving into it with her and setting up a nest.
Winnie also likes to subjugate our cat, Katy, a formerly feral Burmese mix. They have had three or four encounters on the roof of the garage next door, where Winnie alights before flying through our bedroom window.
...
Also,to be thorough..cause i'm like that:
some expert on a question and answer page wrote:Lately my one-year-old white-capped pionus has been making strange clucking sounds. While he is doing this, he is also shaking his wings without opening them and pointing his tail in the air. Sometimes he hooks his beak on the front of the cage while perched.
-- Denise, Butler, Pa.
THANKS for the question! The behavior you describe can mean many different things. It's possible he simply may be trying to get your attention. On the other hand, the tail-in-the-air posture, trembling wings and the clucking point strongly suggest a female bird in the mood. Are you sure your pionus is not a "she"? One year is a bit early for sexual maturity, but she's giving all the signs.