Thank you for your response. The reason I think the other swan is a female is it doesn't even have a knob on it's head. I had read that the males is larger than the females and that held true for the original couple. She seemed to have chosen this mate from a large herd of fledglings about 1/4 mile down the river. They have been defending this territory since. There is a nest and she had been on it about a week. They started to makes nests (seems everywhere) and then stopped (coyotes are all around here, we about the sewer plant, so the coyotes have safe haven), so we assume she got scared and kept moving on untill this one. No we never had them sexed, as we thought the knob was a good indicator?