Something shiny would reflect light back so the bird would know there's something there. Anything hanging in the window to break up the reflection would do.
Oh dear, I posted that silly video without giving previous posts a proper read. My deepest condolences to Kathy G's family and all her falcon friends - and please forgive me if my earlier post seemed out-of-place.
The webcam is now live as they await the return of the ospreys... any time now, they say, but whether The Lady will be among us again, no one knows. We can but hope...