Possible Blackbird nest under decking

Hi I’ve just moved into a new property in Cumbernauld (central Scotland) and we have decking outside our conservatory door.

Recently my dog has been very intrigued at the side of the door under the decking just where the bottom of the gutter is. I’ve set up a camera to detect any motion to see who was coming in and out as originally I thought rats however there has been ‘I assume’ the same blackbird on and off the decking constantly throughout the days. No other movement apart from the blackbird. 

Would they nest under decking? I’m a novice and assumed they would always be up high? Maybe because it’s been so cold this spring so far? 

Advice or information would be greatly appreciated. Thank you.