Sweetgirl does that sometimes, usually if there is any new seed or pellets in the food dishes. She especially likes the sound the expensive pellets make when hitting the bottom of the cage, and they are in dishes too small for her to sit in so it is not that she is trying to nest, just telling me she is displeased with the food selection. She usually stops after a few days. But I put more dishes in the cage with less seed in each and the outside birds are well fed - I throw the seed she has tossed on the bottom of the cage outside on my balcony.