There are several species of owls, depending on where you live in the PNW. I grew up in Oregon and have worked professionally as an Extension agent in NW Oregon for 41 years. I have not heard of a cat or dog being taken by owls. By coyotes, bobcats, raccoons, cougars, etc. ...yes. Owls, no. Chickens are another subject. They can be killed by the predators mentioned above and also by rats, domestic dogs, domestic cats, foxes, weasels, owls, and hawks (and I'm probably missing a few more).

The bottom line is that if you are going to raise chickens, you must build a predator proof coop for the nighttime and either watch them carefully during the day or have a strong, enclosed yard for them to be outside in. Owls and red tail hawks often take the head and leave the rest, depending on the size of the bird. Both owls and hawks are legally protected species and both do a lot of good in ridding areas of field mice and rats. I know of nothing that would scare them away nor should you really try to do so. They are beneficial for the most part.