Birds, Bats, Bees

During a site interview recently, the property manager volunteered, "Oh, look here, it's where the birds nest in the ceiling. I can't really get them out."

Sure enough, there was a decent gap between the soffit and the wall. This gap led to a whole heap of problems, problems that the property engineer couldn't quite solve. 

How do you perfectly seal a space without using ugly caulk or foam? He said he tried using plywood, but it wasn't a perfect fit. So goes the commercial property life.