What is the proper nectar recipe for hummingbird feeders?
Four parts water to one part white sugar. (For instance, one quarter cup of sugar stirred into one cup of water.)
Tap or well water is preferred; do not use distilled as it takes out too many naturally occurring minerals. If you use a water softener, you may want to use partial or totally filtered water; softeners may add too many minerals and salts to the water.
Room Temperature Method: Use very warm water (not hot) right out of the tap. Some brisk stirring is all that is required to dissolve the sugar. Let it cool a bit before setting out a feeder if the sugar water is hot to the touch.
Boiling Method I Some people prefer to boil their sugar solution to retard the growth of bacteria and mold. Use boiling water to mix up the above-mentioned sugar solution; allow it to cool before placing outside.
Boiling Method II Sometimes you may still have problems even if you have been boiling your water; the trouble could be contamination in your sugar. This method should take care of the problem. Mix up the 4:1 water-to-sugar solution in your normal preparation amount. Bring this to a boil on the stove and allow it to boil for a minute or two. Bring more (plain) water to the boil in another container at the same time. Pour the boiled sugar solution into a clean and sanitized measuring container (you don't want to undo your efforts!). If some water boiled off, add plain boiled water to the boiled sugar solution to bring it back up to the original amount it was before boiling. It's a bit more work, but the boiling method tends to extend the 'shelf life' of the sugar solution.
Sugar solution can be made ahead and kept up to a week in the refrigerator.
Discard any sugar solution that has turned cloudy or contains black mold, no matter how 'fresh' the solution is.
Tip: Only fill your feeders with enough sugar solution to last, at the most, two or three days. There is no sense in throwing most of the sugar water away when it goes bad before the hummingbirds drink all or most of it.
If you feed hummingbirds during below-freezing temperatures (yes, you can do this without preventing their migration: see the Winter Feeding FAQ), raising the concentration of the sugar solution to 3 parts water: one part sugar can usually prevent the feeder from freezing up at temperatures around and below 25 degrees F.
For more information about hummingbirds, check out the Hummingbird Garden forum.