Help what has killed my woodpigeon

Hi,  I have a few woodpigeons in my garden,  this morning when I went out there was a load of feathers a foot, no body or bones.  Can anyone tell me what has killed this woodpigeon?  It's not a cat as they only kill the birds not eat them.  Where I live is semi rural 5 mins up the road are fields.  I have big iron gates at the side of the house and iron gates at the front, so it can't be a fox.

Any help would be appreciated as I don't want to loose any more birds.