do you have a size comparison as it cetainly looks like a Blackbirds egg to me to, I found three in the same condition on our lawn from a nest in one of our shrubs after they had been either Magpied. Crowed, Jackdawed, Jayed etc. I also thought it wasn't allowed to put pictures of eggs whatever their condition or nests on here having just had a thread/photo removed, one that had been taken from a very safe distance in our garden
