If the sprite has any problem is with the wings, there's little harmony between bones and feathers(?). Say for example, when the wing is flapped upward, the bones should be flexed in an "S" pattern and the feathers can look falling as they do right now; when the wing starts going downward or soaring, the bones stay straight as they do right now, but the feathers open and generate air resistance, so they should tend to a more horizontal position as they get closer to the wingtip. I know it's a ghost bird, I'm just explaining what "doesn't look right". Otherwise, it is a very good sprite.