Gull

Hi

I am wondering what this bird is. The body looks alot like a juvenile silver gull - which are abundant - but the shape of the head looks a bit odd, and i have not noticed them with bill of this shape and colour.  Maybe its an unhealthy individual.

It was on the banks of parramatta river, in a spot where there is normally a flock of silver gulls, however he was only one there today.

Thanks for any help with the id.