There is a pond by my house (Boston) which is rather large but is almost entirely frozen over. Almost all of the ducks and geese have left given that the open water left is maybe a 30 feet across. There is one swan who's been on the pond all alone for some weeks now, and I'm surprised that she hasn't left. She looks good and is actively going under for food, but is there any way I can tell if she's OK? She's so big and the opening is so tiny. I can only get over there on the weekends, but I try to check on her to make sure she doesn't get stranded if it completely freezes over.

Thanks!