The act in eyes of law likely means owl is actually has chicken in its talons, not simply in the area or looking at one. Similar laws on books for many states but they are trumped by federal law which in this case states you must have a permit that is very hard to get to kill owl. You still have ability to protect chickens, it is just that persecuting the owl is not one of the options. I have relatives that used to go after owls very successfully as you indicate to protect many valuable chickens. In the end either confining birds at night or having dog out with them was more effective than the trap on pole trick.