My name is XXXXX XXXXX I'm a biologist with a special interest in birds. I'm sorry to hear of this problem. Unfortunately, this is the time of year that wasps are attracted to sweet substances. In the spring and summer, they prefer protein sources, but in the fall, they go for sugary things, like hummingbird nectar.
There are several things you can try. If you've never had a problem before, it's likely that you now have a wasp nest somewhere on your property. They like to build nests under eaves, in doorways, and in the beams of garages and other outbuildings. If you find the nest, you can destroy it, but do so carefully. Wasps can be very aggressive, and unlike bees, cans ting more than once. If you find a nest, it would be best to have a professional exterminator take care of it.
Even if you don't find a nest, there are other things to try. Sometimes taking down the feeder for a few days will cause wasps to move on. When you put it back up, put it in a slightly different location. The hummingbirds will still find it, but wasps are more easily confused. Make sure the feeder isn't leaking, as even a small leak will attract wasps and bees. Hanging the feeders in the shade can also deter wasps.
I also recommend a different kind of feeder. There is one called the Hummzinger Ultra which is specifically designed to keep out insects. If they can't get to the nectar, they have no reason to hang around. Here is a reputable online source:
There are also wasp traps of varying prices and effectiveness. Here is a cheaper model:http://www.overstock.com/Home-Garden/Re-Usable-Hanging-Wasp-and-Bee-Trap-No-Chemicals-Needed/5991962/product.html?TRACK=affcjfeed&PID=2647273&AID=10654383&CID=207442&fp=F
Here is an expensive one:http://www.plumbersurplus.com/Prod/SpringStar-YJT-36FD-Oak-Stump-Farm-Yellow-Jacket-Wasp-Trap-36-Pack/208355/Cat/1658?RefID=CJ
One problem with traps is that bees are also trapped, and bees are valuable pollinators.
If you have more questions, let me know in a REPLY. I hope these measures will help with t he problem.
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