Hard to say when it happened, if it is over for good BUT so far, no injured or dead peregrines found or reported in the Winnipeg area. And the nestbox didn't look like a slasher movie so probably an eviction rather than a fight. Princess is a tough bird and this is her nestsite so Sandy was always going to be at a disadvantage. Sandy will probably find somewhere. She was here a bit early, and perhaps she intended to move on after a wee break. Not that she wouldn't have taken over the territory given half the chance, but she knows its occupied, she is very careful to only appear spring/fall when none of the resident birds are around.
And she wouldn't have gotten very far with setting up a "home" in the nestbox, it was frozen solid last Wednesday and has thawed down about halfway as of Sunday. Should be ready for a bit (more) redecorating come mid-week if the temperatures really are above zero as forecasted. Regardless of the temperature, the sun shining into the box all afternoon is really what is doing most of the work.
