When looking for the most effective squirrel-resistant bird feeder, the features that will be most important are a closed-off feeding port, chew-proof feeder material, and a tightly screwed-on lid. Some of the most reputable bird feeder companies offer feeders that shut off the entrance to food and drop squirrels to the ground every time they stand on the perch. Look for weight-sensitive perches or caged bird feeders from brands like Droll Yankee, Duncraft, Perky Pet, and RoamWild. The squirrel-proof bird feeders are only as good as their placement in the yard. If you put any feeder in a tree close to the trunk, the squirrels will find a way to get the seed. It's important to read all the instructions in the package and follow distancing guidelines for clearance around the feeder. Every feeder will be more effective if it is at least five feet off the ground and ten feet away on all sides from any buildings, trees, bushes, telephone poles, or fences.