Odd Bird Call in the Woods

Hello,

New to this.  I live in SW France.  I was walking in the woods this morning and heard a very odd bird call.  I consider myself keen, but not expert by any chance, on the more usual sounds I hear.  I did not manage to record it, frustratingly.  I had never heard this one before.

The Call was a quite long single haunting note.  Repeated after a few seconds.  Medium pitch.  My dog was equally spooked by it.  I saw “something” fly off in the canopy above me, at which point the call became (I assume) an alarm in flight.  A sort of warbling tone repeated as it was flying.  Movement stopped and the long tone reappeared.  What I saw (sorry, no colours other than possibly brownish to report) was medium sized, sort of crow size, but that is a guess.  I do not think it was an owl, but am happy to be corrected.  Certainly not a Hoopoe, which I know well - we have many around us.  Neither was it a Golden Oriole - again, very familiar because they breed in the woods behind my house.

We do get migrants passing by en route to Africa.  I suspect this might be a migrant.

Not much to go on, but any steers would be appreciated.

best regards to all..