What is the best way to harass free roaming cats that stalk our bird feeders?

In our backyard, we don't have to worry about it because our backyard is fenced, and the dogs keep a tight perimeter. However, out front I've recently been spooking cats hiding in the bushes beneath our bird feeders.

I hate putting my dog on a long lead(she gets tangled), but I'm thinking that putting her on a lead out front occasionally could help train the cats to avoid the area. Otherwise, I'm considering trapping them and dropping them off at animal control. Id rather not do this because our city's animal control is overwhelmed with stray cats and dogs, and I don't want to add to their workload.

So if anyone has an effective way they like to deter or harass cats and it's ethical, please let me know!

Thanks.