If you have a feeder that can be suspended off a pole or rafter you could put a squirrel baffle over it. Baffles are like big tin guards that go over (wild) bird feeders- they are an item commonly found at home and garden stores that keep squirrels from climbing down the chain, etc.
Likewise, chipmunks can't climb up very smooth things. Therefore, if you set your feeder as high as possible with the chickens still being able to reach it on something very smooth they would not be able to climb up and get to it. Something like a cinder block on end, surrounded by a smooth tube of sheet metal, or a tall metal pail with vertical corrugations. Plastic might work too- you could try a big smooth bucket with any traction (paper, dirt) stripped off.
The little guys can jump, so set it as high as you can without frustrating/starving your chickens.
Of course, the chipmunks will get the food that was billed out. But that is inevitable.
-MTchick
