Fish heads and tails

We townies aren't very good at wildlife identification, as rubyjones established the other day, but I can safely say this is a black and white, winged fish-eater with orange legs.

"In the port of Amsterdam where the sailors all meet
There's a sailor who eats only fish heads and tails
And he'll show you his teeth that have rotted too soon
That can haul up the sails that can swallow the moon"
- Jacques Brel

(I know there aren't any fish tails, or sailors, and it is only Newhaven harbour, not Amsterdam. And Jacques Brel's not singing either. It's called poetic licence.)