Birds Egg

This should get the brain thinking.
Found in rocks below tide line, possibly washed away by the high tide when the moon was full the other day.
Although you can't see it in picture, the egg is cracked on the underside.
Egg lengh approx 50mm, tan coloured with black markings.
I can think of 2 possible birds that may of layed egg, anyone know for sure what the bird is ???
http://i42.photobucket.com/albums/e3...2/BirdsEgg.jpg

knowing the length and if that is sand clinging to it then it doesn't make it easy, I would say it was an oyster-catcher's egg or possibly a black guillemot's?

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