Keep hummingbird feeders clean to prevent mold and fungus, which can be fatal to hummingbirds. Refill feeders frequently so there is always an adequate supply of nectar for overwintering hummingbirds.   Do not prune shrubs or trees near feeding areas in fall so hummingbirds have plenty of sheltered places to perch and rest between feedings. Bring feeders indoors to warm/ defrost and rotate out with other feeders.

Below are some methods to keep the nectar from freezing:

Photo by: Dan David Cook

• Use a dome to protect from snow, sleet and ice.
• Position the feeder to protect from cold winds and exposure.
• Attach hand warmers to the feeder.
• Heat tape such as used for preventing pipes from freezing.
• Place a clamp-on/ clip-on shop/ work light adjacent to the feeder—about 12-24″ away would be as plumbers do when defrosting frozen pipes. Test the distance before you walk away. Try a 125 Watt infra-red light bulb, but not the red-glass type. Get an I.R. bulb with clear envelope, it casts a more natural light. Connect it all to a timer.
• Place holiday lights around, above or below the feeder.
• Insulate with any fabric.
• Some say to alter the water:nectar ratio, but don’t do this! Keep ratio the same for hummingbird’s health and nutritional needs
• Do not obstruct access to feeding ports. Use common sense and your best judgment.

Information from: hummingbirdmarket.com. http://www.hummingbirdmarket.com/hummingbird_articles/feeding_hummingbirds_in_the_cold.html

And, Seattle Audubon –  http://www.seattleaudubon.org/sas/Learn/SeasonalFacts/Hummingbirds.aspx