A couple of weeks ago one of my Welsh Harlequin ducks got to where she couldn't walk all of a sudden and was pushing herself around with her wings. I put her in a barn stall and was planning on taking her to the vet but the next day she was completely fine and running around. Now, two weeks later, she's doing it again except this time she won't move and is just shaking with her feet stuck out behind her. She doesn't even try to get away from me when I pick her up. I currently have her inside because it's pretty cold outside. Could this be something neurological? They are pinned up at night so I don't know what could've happened to seriously injure her and last time she made a miraculous recovery over night. Any advice would be greatly appreciated!