I was afraid Cody, my cockatiel, would be miserable wearing a collar. It only took him a day to get used to it. The soft material is light weight and non-irritating. The XS size is perfect for a cockatiel. I don't know what one would do with a flighted bird if it needed a collar, but Cody has arthritic wings and can't fly anyway. (The hat is AI; the collar is real)
She mostly refuses fresh food, does eat a bit of freeze dried, refuses anything "wet". Given all of this, I do as much as I can to supplement her diet. I sprinkle on top of her kibble, and she not only accepts it, but if birds have expressions, hers implies that she likes it, and she eats all of her food, so I know she's getting something good,
My bird loves it. We use a very small amount a few days a week to help transition to fresh chop.