This is why I barelly put food in their food bowls. I ONLY put enough food that my birds will eat per meal.
Which means they get 2-4tablespoons of DRY food in the morning(2 tablespoons for moby as he is housed seperately, and Bokka and Opa are together so they get about 4 tablespoons), and THATS IT. And in another dish, a HEAVIER dish, a ceramic dish, is their veggies for the morning (or birdie bread or whatever I dish up for them). They have seed/dry fruits/nuts in their foraging toys.
Then when I get home they get dinner around 5:30-6pm.
They learn that they much prefer to eat what they have then to dump everything.
I prefer ceramic bowls over SS because they are heavier, and bird typically dont tip them also.
So heavier bowls, and not filling the dish all the way up and only feeding enough PER meal, helps a lot.