I am wondering at what temp do you have to worry about the health of a Muted Swan? We have a 1 1/2 acre pond and have adopted/rescued 2 swans last July. It has gotten very cold here (18-30 degrees F) though the pond is not frozen solid....at what tempture do I need to worry about them holding the 106 body temp that they need. I can put straw on the bank for them to rest in at night, but we do have some fox in the area and I am worried that they may be attacked during sleeping time. Do you have any suggestions on housing them safely? They are being fed a corn mixture and plenty of Spring mix, so food is not a concern. They are very freindly, but I do not think I would be able to coax them into the garage or basement at night.