Long Tailed Duck in Harbour

I thought it was quite odd to see this bird resting in the harbour.  It's been around for a few days and I wonder if it might be unwell.  You usually see large flocks of these birds out in the firth as specs on the horizon, so it was great to see it a such close quarters; but....

If anyone out there has seen the Long Tailed Ducks around the harbour before, then please put me right!

Cheers

Seamus