Look on line and buy an ant guard mine is shaped like a bell. They hang on the pole above your feeder. Smear vasoline inside the ant guard and the ants will get stuck and will not make it to the feeder. This will need to be cleaned each time you fill the feeder. Do not put vasoline on out side of guard as a hummer may brush it and get vasoline on them which could keep them from flying. The reason you have fewer hummers may be that someone else nearby has a feeder that is more attractive. This happens to me. While my neighbor is in Florida I get many hummers. When she returns the hummers flock to her. Here is one site for the ant guard, their are several others.
http://www.lnt.com/product/bird-feeders/44247/perky-pet-ant-guard.html