I have a BW Ameraucana who has been leaving me wind eggs for the past 2 years. I have two bowls full of her tiny eggs. I found one in the yard a couple of days ago and it was the tiniest one yet. I'm guessing that she didn't even feel that one come out. She does lay regular eggs, too, but neither kind very often. She is one of my worst layers but she is beautiful & was an excellent broody mama last year so I overlook the infrequent laying.
Oh wow, I'll keep an eye out for tiny blue eggs in odd places then.