Can you advise re some swans odd behaviour towards 1 swan at our public lake? They keep chasing & being aggressive to this swan. They are much bigger than it. I've noticed they're focusing on attacking this swan to the detriment of their own feeding/preening!

The aggressive swans chase this swan round the lake so much they are like stalkers. We were wondering why they behave like this - is it attention seeking/ territorial? Do swans have human emotions (i.e. jealousy)? Or are we giving them human intelligence/ emotions?