Bubbles in droppings

[JesNen]

hello everyone!
I'm just wondering, my parrot Molly has some bubbles in her droppings it's not all the time it's just if she eats some fruit or vegetable, then it goes back to normal but sometimes she can have it without eating any fruit or vegetable. Wonder what it might mean she have been eating antibiotics before for her problems! What do you think it means?

 

[Ripshod]

If the droppings are dropped from a height they can catch some air on the way down producing these bubbles.