How can I keep ants out of my hummingbird feeder?

They make a product called Nectar Fortress. All you need is one little drop on your hook or string and the ants will stay away. You can also make an ant moat. I have some moats and also use some Nectar Fortress as well. here is a YT link on how to make an an moat. https://www.youtube.com/watch?v=DCIX_ifcUrE

What Chubby said is the best advice,but in a pinch, you can wrap double sided tape around whatever the feeder is hooked on so the ants get stuck.When the others see their troop mates stuck they will usually beat feet out of there.

you can buy a product called tanglefoot (check out you local garden center or amazon) and spread it on the base of whatever it is hanging from. It's like very sticky Vaseline. The ants will get stuck knit. It only take a few ants before the rest of the ants learn to stay away.

SPRAY ANT CONTROL AT THE BASE OF THE FEEDER STAND!! OR, PUT CINNAMON OR LEMONGRASS ESSENTIAL OILS ON THE BOTTOM IF THE FEEDER!! HOPE THIS HELPS!!

Spray their hanging post with Pam,the cooking spray.I have mine hanging on Shepard hooks,and have been doing this for years.

Put Vaseline on top of feeder around where the hanger is attached.

http://homeguides.sfgate.com/stop-sugar-ants-hummingbird-feeders-41287.html

If they are coming in from the ground st base of pole use borax soap just sprinkle some around the pole and it will stop them from climbing the pole . If you have it hanging in tree make a paste with borax and place it around the branch and it will stop them also