A mink will take a bite out of anything, and this swan is no different.
As you will see here in this video, minks don't screw around with anything.
When you find something that a mink won't try to eat, let me know. I've even seen things that try to eat the minks, but they end up losing too.
I don't think that the swan lost anything but some feathers, but that mink will be back; bet on it.