We have four goslings which are about six weeks old now; we just took them out of the sheltered tractor and have them in a pen for safety's sake until they get a little bigger. Two of them seem to have trouble with the muscle tone in both wings; they keep drooping. The birds can tighten them up, but then they droop again. They can flap their wings, they seem alert and active, and they're eating well. It's just that their wings droop. We've had geese before and never saw this issue. Any ideas?