At 11.20, MN picked up a group of 10 Little Auks at at range of about 1 mile. Along with this group was an all brown bird which immediately puzzled MN. It appeared identical in size to Little Auk and flew with a typical Little Auk flight, and definitely wasn't another species such as a Starling tagging onto the flock. MN alerted the other observers and eventually PH, WM and TIM got onto the bird. But typically, it almost immediately dropped with the Little Auks onto the sea. After a frustrating 30 seconds, the flock took off again, still containing the mystery bird. It continued to fly north with the Little Auks until disappearing from view to the north.

Size and shape: appeared to be identical to Little Auk.
Flight: the same characteristic low whirring flight as Little Auk.
Plumage: it appeared wholly brown, similar to a Sooty Shearwater brown. The upperwings were not black, but a dark chocolate. The light was good, so all Little Auks were appearing as they should - glossy black above and gleaming white below. The underwings were as the upperwings, very dark. The underparts were wholly brown, but to MN (who had the bird for longer and at up to 60 times magnification), the belly looked very slightly paler. The overall effect was much as a Sooty Shearwater seen in good light. There was no lightening of the underparts either towards the head or to the vent.
Due to the distance, no details could be seen of the head or bill structure.

Immediate discussion talked about the possibility of an oiled Little Auk or an aberrant plumage. An oiled bird was discounted as the plumage was so uniform, the upperparts were brown and there were no paler areas visible on the bird at all. The observers present had extensive seawatching experience of Little Auks, having seen tens of thousands between them, and no-one had ever seen an aberrantly plumaged bird. Whether melanistic birds have ever been recorded is still to be researched.

But what was it? As always with seawatch records, the bird is gone and cannot be checked again. MN considers Crested Auklet to be a possible contender, and in fact, this species has already been recorded in Europe (in Iceland). It is a common North Pacific auklet with a similar distribution to Ancient Murrelet, totally dark plumage at all ages, but is very slightly larger than Little Auk. Other species in contention based on plumage similarities are Whiskered Auklet and Marbled Murrelet, but there are plumage discrepancies with both these species (although PH considered Whiskered Auklet to be a possibility based on size).

Whatever it was, we will never know 100%, but it certainly added a bit of interest to the seawatch.

Observers: M Newsome, P Hogg, TI Mills, W Moss.

Additional notes:
After discussion with several birders with experience of Pacific auklets in Japan, and with other birders with very extensive Little Auk experience, the following further observations on the above record have been made:
hno-one consulted has ever noted Little Auks with anything other than black-and-white plumage.
hCrested Auklet looks noticably chunkier than Little Auk in seawatch conditions and doesn't appear chocolaty brown, but more of a grey/brown.
hWhiskered Auklet always has an obviously visible pale vent area.
hMarbled Murrelet moults into black-and-white winter plumage in August/September.
So we are really no nearer any explanation of what the bird was. Another one to be kept on file under 'unidentified birds on seawatches'...until someone else sees another one.