Well, egg-bound was the first thing I thought of, too, but since she´s already picking up without an egg in sight, it seems it must be something else. I once had one of my gals (the one in my avatar) get chilled (can you believe it!
) during some "cold" weather, nothing like you guys have been getting, it only gets down to about freezing here some nights, and it´s rare, but she got a chill. I kept her up near the house so as to keep an eye on her, as she was shivering and fluffed up and very quiet. I got her to eat something in water with Baytril that I can get here, and after a few days she was on her feet again. I gave her lots of yummy things, and she´s one of the biggest louts down there! Geese are pretty tough, but there are just some things that get them...egg-binding and swallowing trash. I pick up anything plastic etc I find down there that gets brought down the stream, especially after a storm, like you said about.
My hubby has one of those sacks made of woven plastic threads with compost in it...they were busily shredding the plastic threads!! I went and got some wiremesh to cover it to keep them from swallowing it. They´re such terrors!