If you've had her on your shoulder allot she may be holding her droppings ( this s not good for your bird) often birds will hold their dropping while on their flock mates. A way you can avoid this is holding her away from your body (over a place you wouldlike her to poo!)roughly every 15 minutes so that she can have a poo.She may also just have eaten allot in one go. Any way watch her and if they continue to stay large for another day it would be wise to bring her to the vet as like you said some other problem may be the cause (such as an egg). Good luck.