Some people give up and put out ears of corn for the squirrels in an effort to keep them from eating the more expensive sunflower seeds in their hanging tube feeders. About the best you can do is to hang your seed feeder well away from the trunk of the tree. You also need a large Plexiglas dome over the top of the feeder. If the squirrel can't jump up to reach your feeder and he can't jump out, then the only way is down. When they reach the dome, they slip off.
Some feeders have a mechanism that closes when anything heavier than a bird lands on it to eat.
When it is closed, nothing can get at the seeds. This might work. I found an injured bird. The best thing to do is call the local nature center, bird rehabilitation center or the zoo. They will have the local phone number of an organization that can assist you.