Yes they absolutely will kill and eat you ducks and chickens! Especially your ducks because they like to sit out on the ground at night, they don’t roost in a coop like the chicken stew. The owl will sit there and watch until he feels safe swoop down and quickly dispatch, a duck or chicken, mostly ducks as they sleep out in the open, they will eat the head and typically the breast area until they are full and then they will leave the rest if you find a duck dead without a head only it’s possibly a possum they like to eat the head that fills them up and then they’re gone, headless bird of 10 ducks a year due to owl and hawk predation! My solution is knowing that they have to eat too, so I tried to keep plenty hatched out, so I don’t feel the loss as bad but when they kill a grown duck, it tears me up because there’s a lot of money in that duck food and time I also have several motion lights And things that move if they’re triggered by motion, this helps to spook them away, but sometimes I have to resort to firecrackers or just shooting my gun up in the trees in their direction. This will scare them away and make them think twice about coming back, but eventually, they will sneak in and take your critters. Only other option is to put them in an enclosure that has a top over it.! Personally I have a quarter acre area that is fenced in with electric fencing works pretty well against the possums and raccoons and foxes, but I’ve caught coyotes on camera jumping the 4 foot high fence and stealing a chicken and again I occasionally lose birds to hawks or owls. I’m currently experimenting with shelters that the ducks will get under at night. I’m also considering a guard dog to live with them. I don’t want to keep my birds totally caged up. I want true free range and I want the birds to be happy, not a small enclosure so I’m gonna continue to experiment with nonlethal ways to predation. Hope this helps.