In my little flock i have 9 pekin,3 rouen,3 indian runners, and 3 embden geese. We put them in their pen every night and let them out every morning. This has been going on for about 3 months no problems, besides two weeks ago when i was gone for a few days and they refused to go up for my mother but when i returned they gladly went in their pen again the next day. About a week ago we let the ducks out in the morning and they were all there but that night when we went to put them up we were missing our one ruoen female! There were no signs of struggle or anything around the beach and none of the other ducks seemed even slightly injured or upset. we live on a 7 acre lake and during the day the ducks swim around in a tight group, so i assume if there was an attack the other ducks would show signs of it. She was not the smallest nor the largest duck and could fly fairly well compared to the much larger pekins. Once we found her laying eggs in the pen and refusing to get up from them but that only happened once and she never had that problem again. I guess my question is, has anyone experienced something like this before? She just seemed to disappear out of thin air! it is possible that maybe she went off to lay somewhere where we wouldn't take her eggs away? Its been getting into the 20's at night and tomorrow and sunday its supposed to get even colder, I'm worried for her!