We have owls and hawks on the property and neither bother the hummingbirds. I would guess that the hummingbirds would soon get used to the fake one as long as it isn't one of the motorized kind that turn their heads.
I've been thinking about putting up owl boxes to help control the gopher population. A number of neighbors have them and if you get a family of barn owls move in, it is a great method of control as long as you don't mind the pile of bones laying around under the boxes. The only hard part about putting up boxes is the height at which they work effectively. I think it is from 10 to 20 feet for me and with our famous santa anna winds in winter, it would have to be a substantial mounting pole. The height requirement may be different for your species and region.
Deluz, CA usda zone 10a