Wrong again!

I watched this Blue Tit working very hard collecting nesting material and taking it into one of the boxes we have up in the trees. Back and forth, back and forth, it went.

It was only when I downloaded the photos that I saw this . . . !

Now why was he coming out of the box with the same piece he went in with? I can only think that Mrs BT was inside the box and told him in no uncertain terms that he had brought the wrong colour. I wonder if he ever got it right!