You are right, Jo. Agree.
I think this is Tiit! I remember that when the other left, I thought, ahaa.. the male begun to brood. But: I was making picture editions at same time and perhaps could not notice that they changed places. But I thought that the one who returned on the nest about 10:30 was Tiit, ber cause it was this BS who then jumped on the back of the second one..
I looked as carefully as I could what happened then.. yes, the other one has bigger beak! It's Tiit!
(sorry for one hundred times if I am wrong!!)
12:16
edit: here (pic nr 10 from my previous posts) the two beaks can be seen quite well. The angle to both is same and the have almost same position:
10