This is my first instructable! Anyway, I recently moved into a new apartment and having a background in animal behavior, I wanted a bird feeder. But! No matter where I seemed to hang it from, the squirrels were able to jump to it and knock down most of the seeds or break the feeder. They would climb onto the window ledge pictured here and jump at the feeder to knock seeds onto the porch. So this is my solution:
First, this instructable is for deterring squirrels from jumping, not necessarily for preventing any kind of climbing. It also assumes your feeder is hung from some overhanging structure. That being said...
1.) Attain monofilament/fishing line:
Tend to the thinner side as it will be less likely to deter birds as well as limiting an obstructed view of your feeder.
2.) Cut the line to the height of your structure (porch, etc.) and attach a weight of any kind on one end of each length (I used 5/16 nuts)