Long-tailed Ducks

saw a first-winter drake Long-tailed Duck back in mid November but it has been very elusive; then last week I saw a bird with an all black bill so it must be  anew bird but had it replaced the male in the same spot? so two days ago I couldn't find either then one suddenly appeared at the far end of the pit but it dived instantly then another appeared to its left -- an hour later I was sure there were two but it took that long to seen them both up together then I glanced right and there was another close in to the bank! so three Long-tailed Ducks on my patch and today they were all together making things a lot easier; I also had to thank a windsurfer that brought them closer in than usual as they have been typically distant