That shudder they do, mostly ganders! I read/interpret that action as frustration. Gee (white Chinese) does it when he wants corn, lol. I ferment whole corn as a treat and he gets so irritated if I didn't get the bucket out yet! I think of it as a teenage kid not getting what they want NOW.
That may indeed be the answer... he was probably begging for green peas.
Girls- content with some chatting and petting.
Boy- look at me standing here dying of hunger mom!
Silly teenagers! My son was exactly like that not so many years ago.
Oh my, teenage boys sure can eat! The cooler weather, here at least has all my birds eating a lot more feed.