Tu-whit Tu-whoo, I believe, is the sound of 2 owls (female and male) calling to each other through the trees.
At the week-end my brother in law was sorting out some some fencing on the Florida farm when he heard the sound of a bird in a tree overhead and when he looked up into the branches he saw this beautiful owl
Olly (or Molly)
Because of the colour and dark eyes, my guess is that it's a tawny owl. He seemed to be as fascinated by us as we were of him.
Owls have the ability to fly almost in silence so as not to alert their prey, so we didn't hear the other owl take off and fly past us, but oh yes, Olly noticed him/her alright and did that owl thing where he swivelled his head effortlessly around from front to back to watch the second owl fly off into the woods behind him.
We're not sure yet whether they are a mating pair or two males claiming their territory. Either way, there's a strong possibility there may be some little owlets on their way by this summer - let's hope so.