Shortly after we moved here in July 2000 I mounted a bird feeder on a 4 X 4 post and put a piece of used stove pipe on the top 4 feet of it to keep the squirrels off. It worked for quite a few years then one of them learned to drop down from a tiny branch about 8 feet above. Although I promptly sawed it off it seems like ever since it's been a continual competition between them and me.
When we added the porch last summer I had to move the feeder because it was so easy for them to jump to the feeder from the porch roof. I carefully measured how far it was from all the trees around and thought I had it far enough away. However at least one has learned to jump about nine feet from a sturdy oak tree off to the right of the picture below. It's quite fun to watch him climb the tree and spend a fair amount of time adjusting his height and staring at the feeder before making an amazing jump over to the roof where he digs his claws into the somewhat rotten wooden shingles and feasts.
Then Tim noticed when he was here this past weekend that one was also getting to the feeder by jumping up the post and using his hind feet to jump all the way up around the stove pipe. So Saturday I used scrap aluminum siding to wrap the post below the stove pipe and used another two pieces to put an aluminum roof on the feeder.
I'm sorry the quality of this picture is lacking a bit if you look closely you can see that a squirrel is attempting to jump from the ground up to the feeder. I'm happy to say he couldn't make it. The best attempt though I didn't capture with my iPhone. That was last evening when we watched as the squirrel made it's preparations by climbing the tree going through his usual calculations in his walnut sized brain and made a perfect leap to the top of the roof but alas he couldn't get a grip and went sailing straight off the other side onto the ground. It was quite funny to see.
I thought he was going to try it again this morning and I was prepared this time but it seems maybe the pain and embarrassment he experienced last time deterred him from trying again.