Hawks are definitely a threat to poultry. I've only had them take chicks & bantams here, but I have heard others say they've lost full-grown hens to them. The best defense is covered runs. Otherwise, have lots of places for your birds to take cover under, sometimes hanging shiny things helps discourage them too. My chickens have a word they say when anything flies over, they have a special really bad word they shriek when they see a hawk overhead. Everyone in the yard, myself included, stops to look overhead when they hear that said, the little feathered ones run for cover.
But that type of damage, flesh to the tail area, sounds like it could have perhaps been a dog. You could ask on the Predators & Pests section. Could your neighbor have seen a vulture on an already-dead duck? Dogs often like to chew on tail feathers, hawks usually go for other parts, or just carry the carcass away. I'm no expert, but that's been my experience.