Eider Common or Northern?

I was a man on a mission today as there was a bird that I wanted to refind...

On my brief visit to Musselburgh on Thursday I had paused to watch the courting Common Eiders. The conditions were calm and the birds' calls seemed deceptively loud. As I watched them I thought that I should check them for birds resembling borealis Northern Eider, and straightaway I picked up a male showing the distinctive fairy-cake sails. It is the bird on the top left of the picture below - it is just possible to make out one of the sails sticking up from its back. Obviously the range was too far for any decent shots through the DSLR...

I was aware that the identification of this form is far from straightforward but was not encouraged by its bill colour which seemed identical to the other eiders present. On the other hand, this individual did seem to be smaller than the other males. What was interesting was that while this male was indulging in the same courtship display as the other males, he seemed to be actively rejected by the females. Other males were accepted by the females and mating was observed.

Until identification criteria are clarified for this form little can be concluded other than this was an 'Eider with sails'. Whether this is a variant of Common Eider, an intermediate bird or a vagrant Northern Eider can not be concluded although given the number of birds showing this characteristic along the NE coast of Scotland, maybe the latter is unlikely.

I did pass news of this sighting on to the County Recorder on Friday and this clearly encouraged Stephen to check his local patch today. Check out the results here! An identikit lookalike individual if I ever saw one. Now, that just might go to show how common eiders with sails are. Or maybe, just maybe, it is the same vagrant Northern Eider now just a few miles down the coast. After all, despite my searching I certainly couldn't find it at Musselburgh today...