A mystery bird? and the mild misty weather brings in some migrants at Stackpole

The image posted here (wing coverts etc) was found near the path on the eastern arm of Bosherston Lakes - clearly predated by something. Essentially the feathers are dark (blackish-grey)with two distinct white spots on each feather. I have a hunch but what do others think it may be? Click on the image for a closer view of the feathers and the scale

Small flocks of sand martins passed through Bosherston lakes more or less all day to day from mid morning onwards - probably well in excess of 2-300 seen. A couple of chiffchaffs were singing and a firecrest too (though doubtful that it will stay!). Several wheatears about on the coast. A single blackcap was singing near the lakes - (like the firecrest and the chiffs, it could be an over-wintering resident though). Small flocks of redwings also passing through this morning.

Six goosanders are still here on the lakes. A male water rail was also calling and being answered by a female (quite a different call, quite unlike the squeal of the males if you don't know it). The resident green woodpecker also yaffling a lot today. On Monday 15th (sunny) several Commas, small tortoiseshells and peacocks were on the wing too.