We have 2 white swans on the lake. The male has successfully been driving out geese for about 5 years. This year, though, he seems disinterested after a large flock of geese landed on the lake a couple of weeks ago (it's October now). The only difference between this year and the others is that the swans did not produce any offspring this year. I think their eggs were attacked by snapping turtles, or some other predator. Each other year they have had some cygnets survive to maturity.

So, my question is: will the swan go back to chasing geese soon again, or is there something more fundamental going on?