There is a type of feeder that when something heavy like a squirrle lands on the bar it closes it.Pops open as soon as the critter leaves. They are expensive. Lee-Valley carries them and I'm sure bird specific stores do as well.

The only problem with those is that you have to hang it in the right place. If you hang it from a tree, squirrels will quickly learn to hang from a different branch without putting pressure on the closing mechanism, and feast away. I have one, and it works hanging from a Shepard's hook. If they manage to climb the pole, they have to hang on to the feeder which puts pressure on the plate so it closes. I keep the Shepard's hook away from trees, deck, etc., so the squirrels can't jump to, or reach to it. So far they only feed under the feeder. But for more industrious squirrels, you may need to baffle it as well.

My feeders are pole-mounted with stove-pipe baffles. When the baffles are installed properly, they are squirrel proof, so I can hang any type of feeder I want on the poles. The only time that the squirrels were able to get past the baffle was when we had such deep snow last year, that they were able to climb on top the snow and on top of the baffle to get to the feeders (the squirrels had free access last winter!).

The baffles are 2 feet long, I bought them at Wild Birds, but you can make them using materials from the HW store too. They keep off squirrels, all rodents, and raccoons.

These are the same baffles that people often use with nestboxes.

I'm going to have to look into making some baffles. The baffles at WBU are 50.00 and I also need one for my bird house. I haven't even put it up for that reason, and trying to determine the best placement. I may end up having to use my back field, which is a great place, just inconvenient.

You can get the stove pipe cheap at the hardware store. I use the 8" stove pipe baffles on my mealworm feeder and on all the nest box poles.

Wow, their prices have become exorbitant. I just looked up their APS raccoon baffle and it's $44.99. IIRC they cost about $20 or $25 apiece back when I bought 3 of them (5 years ago). I also bought one of the APS systems with 2 hooks. My feeders and the rest of the hardware are all made from hand-me-down or re-used materials.

For me, squirrels will eat anything if they need the food: thistle, suet, safflower. So baffles are a must. I have all of my feeders on poles with baffles. And all of the poles need to be placed away from trees, or anything in which they can jump(chairs, rocks). I use the torpedo baffles which you can find on eBay for $29 (free shipping). I also have the wrap around baffles, again on eBay for $25 (free shipping). I have also made the stove pipe baffles. You can find those directions normally on sites dealing with bluebird monitoring. Good luck. Sometimes the number of squirrels on the ground outnumber the number of birds at my place.

I used the type of feeder mentioned earlier that has a spring to close the ports when a squirrel gets onto the feeder. (Bought mine at Lowe's; about $22.) Worked wonderfully for the 3-4 years I used it in western PA, even though we were at the edge of a woods and had squirrels galore that tried to get into it.
Then we moved to a small town in central OH and I put it up there. Stinkin' squirrels first chewed the plastic off the top part to get at the seed until it got too low for them to reach--then they'd just knock the thing to the ground so the seed would fall out and they would stuff their little selves. Guess Ohio rodents are smarter or more determined than PA ones.
I gave up after the first winter, so now the birds do not get fed--though the squirrels still stay fat on the acorns and black walnuts from the trees in our yard!
I really miss the goldfinches, chickadees, nuthatches...