Duck sounding call... bird of prey neath

 I was in neath area woodland the other day and heard this noise like a duck or goose. Sometimes it sounded like a yappy dog mixed with a goose. Then I saw a bird of prey land on the top of a tall thin tree and do the exact call I'd been hearing earlier on the walk. It flew off to look over the river then landed back on the same tree and did the same call again. It didn't look right for a buzzard and the call wasn't right for what I've seen on YouTube etc. It was dark almost black, probably the size of a buzzard and the hooked bill was almost black. It looked like an eagle and a buzzard in ways, but can't have been an eagle if they are not in Wales, but the call wasn't right for a buzzard from what I've seen online so far and it was way darker than any buzzard I've ever seen. Any ideas? Do buzzards ever look almost black and sound like a duck? It is annoying me !! Annoyingly I thought when I got home it would be an easy id so I wouldn't need to record a duck sound coming from a bird of prey as it shouldn't be hard to find info..I was wrong.
Thanks for any help!