Ants are inevitably attracted to the sweet nectar or sugar water in hummingbird feeders. The most effective way to keep the ants out of the feeder is also the cheapest and easiest. You can make your own ant guard by creating a little moat of water between the feeder and the hook it hangs from. You won't need a degree in engineering or entomology for this simple project, and the ants won't even attempt to cross the ingenious barrier.
Poke a hole in the middle of the aerosol spray can lid with an ice pick or screwdriver. (Note that the lid should be constructed in such a way that there are two separate circular chambers inside.)
Use pliers or a wire cutter to cut the longest piece of straight wire from a clothes hanger. Thread the wire through the hole in the spray can lid, and use the pliers to bend both ends of it into hooks.
Turn the ant guard upside down so that the inside of the lid faces up, and hook it to the hanger you use for the hummingbird feeder.
Pour water into the outermost chamber in the spray can lid. Ants won't be able to cross this ring of water to access the wire leading to your feeder.
Hang your hummingbird feeder on the bottom hook of the ant guard. Check it daily and replenish the water as necessary.