Hummingbirds require disproportionate quantities of nectar or sugar water to fuel their high-energy life style. Flowers provide their food naturally, but when temperatures plummet, these sources dry up or disappear altogether. In these cases, artificial sugar water feeders assume a life-saving role.
How Hummingbirds Survive
Possibly the most fascinating of all birds, hummingbirds delight old and young, bird lovers or not, with their incomparable ability to fly backward and vertically, as well as hover. These high speed acrobatics are achieved through accelerated figure-eight wing beats around 70 times per second. Their tiny heart races, as well, ranging from 250 beats per minute at rest to 1,250 beats per minute in flight, where hummingbirds can reach 60 miles per hour.
The elevated metabolism underlying a hummingbird's kinetic life requires relatively enormous food intake, typically more than one and one-half times the bird's weight in nectar alone each day. The hummingbird's long bill and extensible tongue allow it to probe deeply into nectar-rich tubular flowers, symbiotically pollinating the plant as it feeds. The bird laps up nectar with its tongue, and the nectar is carried to the bird's mouth by capillary action. Sucrose concentrations of hummingbird-favored flower nectar runs less than 30 percent, which is why a 20 percent sucrose concentration (one cup granulated sugar in four cups of water) is recommended for home feeders.
A second important element in a hummingbird's diet is invertebrate prey. Hummers eat small insects, spiders, ants, caterpillars and arthropod eggs, and will even poach trapped insects from spider webs. Hummingbirds observed hovering in mid-air or zipping to and from a perch are almost certainly picking off flying insects. Sapsuckers unintentionally provide both types of food for hummingbirds, as well. Sapsuckers tap the phloem sap in tree bark to feed on the sugar-rich liquid that approximates the sugar content of flower nectar. Insects are also drawn to the flowing sap, and hummingbirds visit these wells for both sap and insects. High-calorie nectar or sugar water is the more dominant part of their diet, but protein-rich insects are also important. Unfortunately, when temperatures plummet unexpectedly, both of these food sources are impacted.
Hummingbirds and Cold or Freezing Weather
Most North American hummingbirds avoid the coldest weather extremes by leaving their northern breeding grounds before winter arrives, migrating to Mexico or further south. Many hummingbirds, however, live year-round in milder U.S. zones, such as California and Arizona, and, increasingly, some birds that typically migrate to Mexico, such as Rufous Hummingbirds, are wintering in the southeastern U.S. Additionally, some birds remain in northern areas or delay migratory departure past the arrival cold weather. Contrary to earlier belief, keeping artificial feeders available does not delay migration, and in migratory areas such as the midwest and eastern U.S., feeders should not be removed until two weeks after the last hummingbird sighting.
When late-departing migrating hummingbirds are surprised by cold weather, or when abnormally freezing weather hits resident hummingbirds in temperate states, intervention by birders can be life-saving. Hummingbirds survive the night by ingesting copious amounts of nectar at dusk and storing this reserve in their crops and digesting it throughout the night, during sleep. In extremely cold conditions, hummingbirds can drop into a hibernation-like state (torpor) which conserves energy through reduced heart rate, breathing and temperature, but which also increases the birds' risk to predation. Birders can help hummingbirds during these extremes by providing plenty of sugar water, and by insuring that this food stays unfrozen.
Sugar water in feeders will remain liquid at 32 degrees Fahrenheit, the temperature where plain water freezes, but if temperatures drop much below this level, even sugar water will freeze. Higher concentrations of sugar to water lower the freezing point, but become difficult for hummingbirds to ingest, and are not recommended. Consequently, birders must monitor the feeders closely. If temperatures are forecast to fall below freezing overnight, feeders should be brought indoors after dark, after birds have quit feeding, and rehung at the earliest light, before hummingbirds begin feeding. If temperatures remain below freezing during the day, feeders should be taken indoors and thawed once ice crystals appear. An all-plastic two-cup feeder, such as the First Nature model 3051, is ideal for this purpose, since it can easily be thawed in a microwave. Be careful not to overheat the sugar water. A two-cup feeder normally can be thawed in less than one minute in a microwave. Hummingbirds appear to become more aggressive than usual during extreme weather, as well, suggesting that more feeders, and more dispersed feeders will provide better opportunities for all the birds.
Helping Hummingbirds During Freezing Weather
In early February, 2011, much of the U.S. was hit by arctic air. In southeastern Arizona, where Costa's and Anna's Hummingbirds are common throughout the winter, early morning temperatures dropped to the mid-teens and below, impacting insects and flowers. Artificial feeders became critical to hummingbird survival, and even these would freeze solid if unattended. Fortunately, bird lovers across the area stepped up and kept feeders filled and thawed. Freezing weather is unavoidable, but when it comes, a little effort on our part will make a world of difference to our hummingbirds.
For more information about enjoying and feeding hummingbirds, see the following articles:
- How to Make, Store and Use Hummingbird Food
- Which are the Best Kind of Hummingbird Feeders to Use?
- Where Should You Hang Hummingbird Feeders?
- How Many Hummingbird Feeders Should be Hung?
- The Costa's Hummingbird
- Why a Sapsucker may be a Hummingbird's Best Friend
Bob Bowers - A lifelong naturalist and amateur ornithologist, Bob's avocation is studying, photographing and writing about birds.
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