What is this?

Apologies for the poor quality of the photo, but I've been scratching my head as to what it could be.

The photo was taken back in March, though I've been a bit busy the last couple of months, with work, family and hospital matters, all positive I'm happy to report.

My guess is probably an owl, though it does look a little like a grey squirrel, a wild guess would be cat due to the fury look of the tail. It was taken using the 600mm lens at full range, 

Whatever it is, it's roosted among the trees where a lot of herons reside.