There's been a pair of mute swans on our local lake for the past 3 years. 2 years ago their nest was trashed and eggs smashed by persons unknown. last year they successfully raised 2 cygnets from 6. Last Wednesday I noticed she had laid 2 eggs and the pair were busy adding to the nest. But on the Thursday I noticed the nest empty of eggs and the female no longer anywhere to be seen. The male was swimming close to the nest. The female hasn't returned and I'm fearing the worst (human interference). The male is now sitting on the nest looking rather disinterested and certainly isn't interested in feeding.

My question is could there be another reason for the female to leave?