Well, I chucked a mug of hot tea (what a waste) at a black cat that was stalking the area around my bird feeders earlier today, does that count? (It probably didn't work, I picked up a dead robin late this afternoon, it may have been another cat though.)
If you are having a problem with cats around the feeder, get a cheap water pistol. When they get sprayed with water enough times, they'll associate the feeder with something unpleasant & will avoid your yard. Doesn't hurt them & saves you from breaking a mug.
That is the advice from the cats protection league too. Sadly, like most people, I don't carry a water pistol around with me, and, whilst in the past I have had one "primed and ready" to use, by the time I have gone to get it, the cat will have made off (sometimes with bird, still alive in its mouth). If you throw what you already have in your hand, you stand a much better chance of scaring the vermin off.
The only thing which really works (and I have been trying to stop cats killing birds in my garden for 20 years) is to scatter around chilli powder. The trouble is, I know that IS cruel, and it also affects hedgehogs badly, and they are in extreme decline in the UK.
Yeah, my next suggestion would have been chili pepper or ground crushed red pepper sprinkled around the feeder.
I've had to deal with this problem in the past. Some other suggestions: Change where the feeders are located so they aren't near anything a cat can use as cover. Make sure the feeders are at least 5 feet away (preferably 10 feet away) from plants & shrubs so the cats don't have any place to hide and the birds will be able to see any threat coming. If you can't do that, you might want to consider putting in some decorative or thin flexible wire fencing around the plantings. It won't take away from the beauty of the plants but if a cat decides to hide in the plant, the fencing will keep it from being able to attack. I don't know if your garden area is large or is surrounded by a fence but if you can, you might want to consider fencing it off altogether to make it more difficult. If it is already fenced off, you might want to buy chicken wire and run it all along the fencing, making sure you cover any gaps or holes that a cat can get through.
Barring all of that, you can also install feeders that deter both squirrels & cats. Ones that are too high to get to and have barriers on them. You hang them either from a high branch or on a tall shepherd's hook. I found some examples ( click on the links on the page) http://feedingthebirds.com/cat-proof-bird-feeders/
I just did a search to see if there were any other ideas and found some great advice on dealing with feral cats. Scattering broken egg shells or sharp pebbles! I never thought of that. There are other suggestions on this link: http://birding.about.com/od/birdconservation/a/Discourage-Feral-Cats.htm
Yep, tried all that. I very expensively "cat-proofed" my fencing a few years ago. They just climb over the top. The feeders themselves are fine, but of course, most British garden birds are ground feeders anyway. Blackbirds, Robins, Dunnocks, Thrushes, Sparrows, always try to feed on/from the ground, even if they take food from a feeder.
The latest figures from the RSPB (who curiously do not condemn the cats or their owners) suggest that 8,000,000 birds are killed by domestic cats, many of those birds are on the endangered list.
My garden is visited most days by three different local cats, occasionally a fourth joins them.
I have pretty much given up, as most people have to in the end.
I'm sorry it's such a problem where you live. Have you tried wrapping the branches in aluminum foil or chicken wire? They won't walk on aluminum foil believe it or not. And, if you can wrap chicken wire near the trunk of the tree high enough up (like a six foot area) that discourages them from climbing too.
I'm now in a very rural area and it's always annoyed me that many of my neighbors allow their animals to run loose. It's dangerous. We have people that drive like maniacs on our roads & we have all sorts of wild animals that are looking for anything they view as food (hawks, owls, black bear, coyotes, fisher cats (weasel type of animal - very vicious & nasty),... Unfortunately, over the years, these people have learned the hard way about keeping their cats inside. Some still don't care. They just get another cat.
Have you thought about getting motion activated sprinklers? We used these to get rid of the neighbor's dogs who seemed to be trained to use our front yard to do their business in. Worked wonderfully. I think they were look like $50. And work whether you are home or not.
Benedict Arnold 