Hello! There are two swans at a lake we camp at all summer. One of them is tagged and was actually released here two years ago. The two swans have gotten along great the last month or so since they arrived after winter. They've even started building a nest. We know that the swan that is tagged is a male. We are just assuming that the other is a female. While the male is busy building on the nest, the other swan does a lot of preening.

In the last day or two, the attitude of the male has completely changed. He has gotten aggressive towards the female, hissing at her and chasing her. Do you have any idea why he would have this recent behavior? Thank you!