Search of the Week: “what can I feed hummingbirds to get them protein”

salvia-flowers

Sugar water is a substitute for the nectars of hummingbird-pollinated flowers, which provide the birds with energy-rich sugars, water, some electrolyte salts, and little else. Almost everything else their bodies need, including protein, comes from eating insects, spiders, and other small arthropods. (Salvia sp. in my garden, copyright S. L. Williamson)

Hummingbirds do need extra protein in their diets during the nesting and molting seasons. Here are some tips for helping them meet their protein needs:

  • Don’t use broad-spectrum pesticides in your yard: Many common yard and garden pests, including aphids, whiteflies, and various annoying gnats and midges, are just the right size for hummingbirds to eat. Even if the birds don’t sicken and die from eating poisoned prey, spraying pesticides destroys an essential source of natural nutrition and makes your yard less attractive to them. Switch to targeted, low-risk remedies for specific pests, such as a hard spray of water under leaves for aphids and various forms of the natural pest pathogen “Bt” (Bacillus thuringiensis) for caterpillars and mosquitoes. Also, beware of purchasing hummingbird flowers from mainstream garden centers. Many of these plants have been unnecessarily treated with the same neonicotinoid pesticides that have been implicated in the terrifying declines of honeybees, native pollinators, and native insect-eating birds.
  • Cultivate a compost pile: Fruit flies are attracted to decaying vegetable matter, including fruit rinds and scraps. Garden experts often advise against adding fruit to compost piles/bins in part to discourage fruit flies, but these tiny insects provide excellent hummingbird food while aiding the composting process.
  • Grow your own fruit flies: There are lots of recipes on the Web. When a culture matures, just set the container in your garden and open it so the flies can escape.

The one thing you absolutely, positively should never, ever do is add protein supplements to your feeder solution. It’s unnatural, the solution will spoil much faster, and the birds will not like the taste. (Captive hummingbirds drink protein-rich liquid diets, but only because they have no choice. They’d much prefer flower nectar or sugar water for energy and water and a variety of insects and spiders for protein, amino acids, vitamins, minerals, etc.)

More on what to put (and not put) in your hummingbird feeder:

Feeder Solution Evolution, Part I: The Basics
Search of the Week: “is molasses ok to feed hummingbirds”
Feeding Hummingbirds: The dangers of red dye
Beet juice in hummingbird feeders: NO!
Search of the Week: “hummingbirds won’t eat instant nectar”
Search Roundup: Feeding hummingbirds
Keeping hummingbird feeders clean

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Keeping hummingbird feeders clean

Hummingbird Feeder Cleaning Kit

Brushtech Hummingbird Feeder Cleaning Kit at Amazon.com (click image)

If you’re like me, you’ve got a collection of toothbrushes, baby bottle brushes, and even well-washed mascara brushes sitting next to your kitchen sink for cleaning hummingbird feeders. The problem is that tools made for other cleaning jobs don’t always work as well for such a specialized task, so it’s nice to see a set of brushes made especially to reach the nooks and crannies of typical hummingbird feeders. The big brush in this set could even get into the enclosed bases of some of the cheapo feeder models to remove crud you can’t see.

Of all the nasties that grow on hummingbird feeders, the nastiest and hardest to control is black mold. A 15-minute soak in a dilute solution of chlorine bleach*⇓ (1 part bleach in 10 or more parts water) is very effective at killing black mold on non-porous surfaces, but an hour-long soak in white vinegar is a less toxic alternative (NEVER use bleach and vinegar together: you could kill yourself!). In either case, follow up the soak with a thorough brushing to remove dead mold colonies and other organic growths, then rinse well and let the feeder dry before refilling to allow the odor to dissipate.

An even safer mold killer that’s much kinder to your nose than bleach or vinegar is 3% hydrogen peroxide, the medicinal kind you can buy in any drug or grocery store. The downside is that it’s much more expensive than bleach or vinegar. A frugal alternative to traditional soaking is to add a couple of ounces to the feeder bottle, screw on the base, invert the feeder and swirl gently over a sink or bucket to make sure the peroxide covers all inside surfaces, then allow it to stand for at least 10 minutes. While the peroxide is doing its work from the inside, spray the outside with more peroxide to kill any mold growing there. Follow the treatment with a good scrub, including the ports. and rinse well to remove any debris. No drying needed; the peroxide will leave no odor, and the only residues are water and oxygen.

This advice applies mainly to bottle-style feeders. Saucer feeders such as the Aspects Hummzingers can be cleaned by hand using dish detergent and the small port brush in the kit above or washed on the top rack of the dishwasher. If any stubborn debris accumulates in the built-in ant moat, the little ball-shaped brush in the Brushtech set will swish it away.

Regardless of what type of feeder you have, it will need cleaning and refilling every 1 to 3 days in hot, windy, and/or rainy weather and every 4 to 6 days in cooler, calmer, drier weather, whether the birds have emptied it or not. If you can’t make a commitment to good feeder hygiene, it’s best to plant flowers instead.


* There’s a persistent myth that using chlorine bleach to clean feeders will kill hummingbirds. It won’t as long as you rinse the feeder well, just as you would if using bleach to disinfect your own dishes or your pets’ dishes. Any minute traces of chlorine residue will be rendered harmless by reacting with the sugar in the feeder solution (the same thing happens when you mix sugar with chlorinated tap water).

Rethinking winter hummingbirds

This post is adapted from an article that originally appeared in 2010 in my “Out the Window” column in WildBird magazine. Though the focus is vagrant hummingbirds of migratory species, many of the issues apply equally to semi-migratory hummingbirds such as Anna’s that have expanded their range into areas where winter survival depends on feeders. 

Anna's Hummingbirds are the most cold-tolerant of any North American species, but even they can't survive extended periods of subfreezing weather without help from their human hosts.

A hungry male Anna’s Hummingbird fills his crop moments after a thick layer of fresh snow was brushed off the feeder. Anna’s are the most cold-tolerant of all North American hummingbirds, but even they can’t survive extended periods of subfreezing weather without help from their human hosts.

For more than 20 years I’ve been telling people that it takes more than a bottle of sugar water to keep a healthy hummingbird on the breeding grounds when its instincts tell it to head south. Though that’s still true, it doesn’t apply to the increasing numbers of vagrant hummingbirds whose instincts lead them not to the tropics or the relatively mild southern and coastal parts of the U.S. but to cold latitudes where their chances of long-term survival are slim.

In some cases, these seemingly lost and doomed migrants do make it through the winter with a little help from their human friends, even surviving to return the following fall. It’s the less fortunate ones and the dilemmas they pose for their hosts and admirers that caused me to rethink my longstanding advice to leave hummingbird feeders up in fall.

The vast majority of wild birds live and die without a single human ever taking a personal interest in their welfare, but hummingbirds aren’t most birds. Their deceptive daintiness and apparent dependence on our gardens and feeders trigger much stronger and more complex emotions in us. Small wonder, then, that firestorms of controversy often erupt over whether, when, and how to help vagrant hummingbirds that are struggling to cope with brutal northern winters.

Unfortunately, there’s no one-size-fits-all approach to dealing with tiny birds in trouble. A hands-off policy, as heartless as it may seem, would be the logical choice if wintering hummingbirds were getting by entirely on natural resources. Once artificial feeders and the people who tend them enter the picture, “letting nature take its course” is no longer an option. It’s not so easy to talk about natural selection when you have to look that hummingbird in the eye each morning as it huddles on its slushy feeder.

Intervention has its own hazards, even when left to licensed experts (as required by federal law). The “Three Rs”— Rescue, Rehabilitate, and Release—may fail if delayed until the bird is too weak to survive the stress of capture or if the specialized care it needs is unavailable. Some wildlife rescue groups are reluctant to take in hummingbirds because they don’t have the expertise or resources to provide proper care.

New problems arise when the rescuers decide to add a fourth “R”: Relocate. It was once common practice to capture vagrant hummingbirds, even those in no obvious distress, and fly or drive them hundreds of miles to warmer climes. As we learned more about hummingbird migration, we realized that in most cases this is a spectacularly bad idea. Like many other birds, hummingbirds learn the particulars of their migration routes by experience. Without that experience, a bird that manages to survive capture and relocation may end up permanently disoriented. Release at or near the original rescue site allows the bird to reorient itself to familiar landmarks in preparation for the next leg of its journey, whether further south or back towards its breeding grounds.

When to release a rescued hummingbird can be just as important as where, especially for early-migrating species such as Rufous and Allen’s. Their northward migration along the Pacific Coast is well underway in January and February, when much of the U.S. is still in the grip of winter. Releasing a hummingbird in the dead of winter isn’t as crazy as it may sound. Some of the tougher species have been observed to hang on through blizzards and ice storms only to move on once the weather cleared.

This Pine Warbler is no better adapted to winter weather than most hummingbirds, but few people would advocate capturing it for relocation or incarceration in a zoo.

This Pine Warbler is no better adapted to winter weather than most hummingbirds, but few people would advocate capturing it for relocation or permanent captivity.

Another misguided approach is to sentence “defective” hummingbirds to life in captivity. Though modern zoo ethics discourage taking wildlife out of the wild, this was exactly what happened to a Green-breasted Mango that found its way to southern Wisconsin in the autumn of 2007. This spectacular bird, only the second member of its mainly tropical species ever seen north of southern Texas, was preemptively rescued ahead of a winter storm and transported to a wildlife rehabilitation center. Against the advice of numerous hummingbird experts, center officials decided to turn the bird over to the Brookfield Zoo in Chicago. Members of the hummingbird community lobbied for the bird’s release either back in Wisconsin or in the lower Rio Grande Valley of Texas, but zoo officials were determined to add this avian celebrity to the collection. The following fall a late-migrating Ruby-throated from Michigan ended up at the same zoo under similar circumstances, again against the advice of experts.

How do we keep hummingbirds out of these predicaments in the first place? One simple change in your feeder routine could make a huge difference. Switching to a sugar-water ratio of 1:3 by early September, when high-risk birds may be passing through, will help your visitors put on fat more efficiently while still providing essential water. The higher sugar content also lowers the solution’s freezing temperature without making it too syrupy for hummingbirds to drink, so it’s the perfect recipe for winter feeding as well. Most hummingbirds take to the sweeter solution right away, but you can gradually increase the sugar content over several days to avoid alienating your regular clientele.

Of course, the ultimate solution to the problem is to stop feeding hummingbirds before winter sets in. If you live north of USDA Plant Hardiness Zone 7a  (average minimum winter temperatures 5 to 10̊ F.) and would prefer not to take on the responsibility of hosting a wintering hummingbird, simply take down your feeders within a week after before the first frost or by mid-October, whichever is earlier, even if there are still hummingbirds around. You’ll still be providing a boost to tardy migrants without encouraging any wayward travelers to consider your yard as a possible winter refuge.

* With increasingly erratic weather resulting from global warming, some areas with long, cold winters are experiencing first frosts later in the fall, after most hummingbirds have reached their winter destinations. Taking feeders down while natural resources are still abundant provides a less abrupt transition for any lingering birds and may increase their chances of survival, at least in the short term. [updated 11/30/16]

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Search of the Week: “can hummingbirds drink water heated by the sun”

Rufous/Allen's hummingbird at feeder

A young Rufous/Allen’s hummingbird drinking on a hot summer afternoon.

Of course they can, as long as it’s not straight out of a solar water heater.

But don’t take my word for it when you can easily prove it to yourself. Leave your hummingbird feeder in full sun for a few hours on a hot summer day, then check the temperature of the sugar water.

Unless you’ve hung your feeder near a highly reflective surface and/or inside an enclosed greenhouse-like space, the liquid won’t be much warmer than the surrounding air. This is because a relatively small small volume of liquid in an uninsulated container loses heat to the surrounding air about as fast as it gains it.

Hummingbirds are not delicate, fragile creatures. If the feeder solution isn’t hot enough to damage human skin, it’s not going to burn their tongues.

Addendum, June 23, 2014: A complete answer to this question involves numbers, and I finally got around to getting some on a hot afternoon here in the high desert of southern Arizona:

  • Air temperature in full sun: 95° F. (35° C.)*
  • Feeder solution temperature in full sun: 105° F. (40.6° C.)*

For comparison:

  • Hummingbird body temperature: ~104° F. (~40° C.)
  • Highest air temperature ever recorded in the U.S.: 134° F (56.7° C).
  • Optimum hot beverage temperature: 136° F (57.8° C).
  • Water hot enough to cause third-degree burns to human skin in 5 seconds: 140° F. (60° C.)
  • McDonald’s coffee, pre-lawsuit: 180–190° F. (82–88° C.)

* Air and sugar water temperature measured with a cooking thermometer in my yard at around 2 p.m.; the feeder is a fancy HummZinger with a translucent top, which probably adds a little greenhouse effect to the direct solar heating.

References:

LiveScience: What’s the highest temperature ever recorded in the U.S.?

Brown F., and K.R. Diller. 2008. Calculating the optimum temperature for serving hot beverages. Burns Aug;34(5):648-54. Link (PubMed)

Wikipedia: Liebeck v. McDonald’s Restaurants

The Burn Foundation: Safety Facts on Scald Burns

Search of the Week: “is molasses ok to feed hummingbirds”

Image

Feeding stations in southeastern Arizona attract rare beauties such as Lucifer Hummingbirds with plain old sugar water.

NO. Molasses (and brown sugar, which contains molasses) is absolutely not safe to feed hummingbirds. It’s high in iron, for which nectar- and fruit-eating birds have a very low tolerance. When hummingbirds consume more iron than their natural diet provides, the excess builds up in their organs and kills them slowly and painfully.

As I’ve covered here before, there are only two things that are absolutely safe to put in your hummingbird feeders: white sugar and water. Just add 1 part white granulated sugar to 4 parts good quality water. Stir until dissolved (no boiling necessary). Adding to or substituting for this recipe could put their health at risk, and what intelligent, caring person would want to do that to a hummingbird?

But since there have been so many searches like this lately, let me repeat and expand the list of things that don’t belong in hummingbird feeders:

No-sign-20px Honey
No-sign-20px Molasses
No-sign-20px Any non-white sugar, including brown, organic, “raw,” turbinado, “natural,” Zulka Morena, colored baking sugars, and evaporated cane juice
No-sign-20px Powdered sugar (which contains anti-caking ingredients)
No-sign-20px Pancake syrup, maple syrup, or agave syrup (misleadingly marketed as “nectar”)
No-sign-20px High-fructose corn syrup (e.g., Karo Syrup)
No-sign-20px Artificial sweeteners (Sweet ‘n’ Low, Equal, Splenda, or their generics)
No-sign-20px Natural nonnutritive sweeteners (stevia derivatives such as Truvia, Stevia In The Raw, various others)
No-sign-20px Anything containing artificial or nonnutritive sweeteners
No-sign-20px Artificial food coloring, including but not limited to Red #40 and Red #3
No-sign-20px Anything containing artificial coloring (including most “instant nectar” and “hummingbird food” products)
No-sign-20px Anything containing sodium benzoate or other preservatives (including most “instant nectar” and “hummingbird food” products)
No-sign-20px Protein or vitamin supplements (protein powder, pet bird vitamins, dried insects, etc.)
No-sign-20px Jell-O or similar products
No-sign-20px Kool-Aid, Crystal Light, or equivalents
No-sign-20px Gatorade or other sports drinks
No-sign-20px Alcoholic beverages of any kind
No-sign-20px Carbonated beverages of any kind
No-sign-20px Caffeinated beverages of any kind
No-sign-20px Fruit juices (except a small amount of concentrate added to sugar water for color, if you must)
No-sign-20px Beet juice or other vegetable juices
No-sign-20px Lemonade, limeade, or other fruit-based beverages
No-sign-20px Coffee, regular or decaf
No-sign-20px Teas, whether black, green, or herbal, regular or decaffeinated
No-sign-20px Dairy products or substitutes
No-sign-20px Vegetable oils
No-sign-20px Soup, broth, or consommé
No-sign-20px Vanilla extract or other natural or artificial flavorings or extracts
No-sign-20px Essential oils or herbal extracts
No-sign-20px Perfumes or other fragrances, whether natural or artificial, designer or fake
No-sign-20px Colloidal metals, including silver, gold, platinum, uranium, plutonium, and unobtanium
No-sign-20px Anything other than pure white granulated sugar and good-quality water. 

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Beet juice in hummingbird feeders? NO!

In Arizona’s White Mountains, hummingbird swarm a feeder filled with colorless sugar water. Coloring of any kind is unnecessary, and the quantities hummingbirds consume increase the health risks of artificial dyes.

A colleague recently contacted me via Facebook to ask if beet juice might be safe if used to color sugar water in hummingbird feeders. I made the mistake of saying “probably” before doing enough research. After reading up on the nutrients found in beets, I’ve got to say “NO!

For decades, hummingbird experts have denounced artificial dyes as unnecessary, unnatural, and potentially harmful, but it’s tough to override the public image of a feeder filled with jewel-like red liquid. As frustrating as it is to see people still coloring their feeder solutions, it’s encouraging that some are looking for benign alternatives to artificial dyes.

The natural coloring I usually recommend is a few drops of raspberry, cherry, or cranberry juice. The pigments in these fruits are antioxidants called anthocyanins. Beet pigments, called betalains, are also antioxidants and are found in cactus fruits and pollens, so they’re something hummingbirds might ingest naturally (though in vastly smaller quantities than they’d get from a regular diet of beet-red sugar water). The problem is that beets are also a good source of iron. That’s not a problem for most humans, but it is for hummingbirds and other nectarivorous birds, as I explained in Feeder Solution Evolution Part I. Vegetable-based dyes made from beet pigments are purified, so you wouldn’t expect much iron to remain. Just juicing or boiling beets runs the risk of extracting deadly iron along with desirable pigments.

Even without the iron issue, there’s a potential stumbling block in the unsubstantiated/undebunked rumor that hummingbirds don’t like beet sugar. If that’s true, then they almost certainly wouldn’t like beet juice, either, since it would contain far higher concentrations of the bitter-tasting saponins blamed for this reported preference.

A Viceroy enjoys the juice of an Englemann’s Prickly Pear fruit.

The good news is that the betalain-rich fruits of some prickly pear cacti (called tunas in Spanish) are much lower in iron than beets (Englemann/Lindheimer Prickly Pear found over most of the Southwest. If you’re lucky enough to live where this species is native, you can harvest ripe tunas using barbecue tongs. Wash thoroughly (wear gloves!) before cooking or juicing to remove dust and spines, and filter the resulting juice to remove any stray spines and other solids that might contribute to fermentation of your sugar water.

The juice will keep over the winter if you freeze it in ice trays and store the cubes in plastic bags in the freezer. Then it’s easy to pop a cube into a fresh batch of sugar water (make large batches or use small cubes—it doesn’t take much to give the liquid a bright color). You can also use the juice to make jelly and syrup, color and flavor lemonade and gelatin, or add a desert touch to your Thanksgiving celebration.

One last issue with betalains in hummingbird feeder solution is that they might perform differently depending on the quality of the water used. These pigments are pH sensitive, turning reddish in acidic solutions and bluish in alkaline ones just like litmus paper. If added to normal tap or bottled water, which is typically neutral to slightly alkaline, prickly pear juice will turn purple to violet. It won’t matter to the birds, of course, but it might take adding a few drops of lemon juice to the solution to get a color similar to that produced by artificial dyes.

What a lot of trouble. Why not stick to plain sugar water?

Related posts: Beet sugar: Maybe a myth, but not debunked Search of the Week: “is molasses ok to feed hummingbirds” Search of the Week: “if refined sugar is so bad for us, then why do we feed it to hummingbirds??” Feeder Solution Evolution Part I: The basics

When the going gets chilly, the chill get crafty

hand-crocheted humingbird feeder cozy

My hand-crocheted hummingbird feeder cozy

After posting a bunch of second-hand/theoretical advice for keeping hummingbird feeders from freezing, I found myself and my clientele (several Anna’s and a Violet-crowned or two) facing a forecast low of 13º F. (-10º C.). My northern friends will smirk (and rightly so), but this is southern Arizona for peeps‘ sake.

Since temperatures this low are such a rare event here, insulating the feeder seemed like the most sensible (and cheapest) approach. Besides, my crochet hooks had been collecting dust since last fall, and this was a good excuse to get back to hooking. So to speak.

After a quick stop to shop for appropriately colored yarn and about two hours of hooking, unraveling, and rehooking, I had a crocheted feeder cozy for an 8-oz. Nature’s Best (my all-time favorite bottle feeder that’s no longer available, sadly).

Before calling it a night, I filled a clean feeder with hot 3:1 solution, slipped on the cozy, and stumbled across the starlit yard to hang it in one of the more popular spots. Another Nature’s Best that had been out all day had frozen beyond the Squishee stage already, with a band of syrup trapped between solid layers of ice.

When I finally got around to checking the feeder this morning (about an hour and a half after sunrise), there was no ice in the bottle at all, but swirls of denser syrup indicated that at least some of the solution had frozen. Interestingly, the HummZinger Mini hanging in front of the poorly insulated living room window showed no signs of having frozen, despite containing a smaller volume of solution with larger surface area and getting very little morning sun to warm it up (it’s on the north side of the house).

I was a little worried about how the hummingbirds would respond to the weird appearance of their feeder. The female Violet-crowned Hummingbird didn’t seem the least bit put off by the bright red “sweater,” but then she didn’t have to wear it.

Related posts:

Keeping hummingbird feeders from freezing

Helping hummingbirds through winter weather

Keeping hummingbird feeders from freezing

Two winters ago I posted some suggestions for helping hummingbirds through winter weather, including boosting the sugar content of the feeder solution, taking advantage of heat radiating from windows, creating shelters, and using heat lamps. A lot of people are dealing with frozen feeders already this season, so here are a few more suggestions gleaned from the winter hummingbird community:

  • Make a “feeder cozy” to help fresh solution retain its warmth longer. It can be as fancy as you like—knitted, crocheted, quilted, down-filled—but pipe insulation (fiberglass wrap or foam tube) or a section cut from a discarded blanket or sweater will do the job. If it’s roomy enough, you may even be able to tuck handwarmer packs inside. [A commenter on BirdForum mentioned using stockings; if your feeder bottle is small enough, a heavy wool sock would make a quick and easy cozy.]
  • Wrap your feeder in outdoor-rated incandescent Christmas lights (the old style, not energy-efficient LEDs). The bulbs should produce enough heat to keep the sugar water slightly above air temperature, especially if you add an outer layer of aluminum foil to reflect heat and block wind.
  • Wrap your feeder in pipe heating tape under a layer of insulation. Thermostatically controlled models will save energy by turning on as necessary to keep the solution just above freezing.
  • Invert your sugars. The freezing point of a solution depends on the number of molecules present. More solute (sugar) molecules make it harder for the solvent (water) molecules to link up. Inverting your sugar, which breaks each sucrose molecule into one of fructose and one of glucose, doubles the number of molecules and depresses the freezing point by a few additional degrees without adding additional sugar.

To invert ordinary table sugar, combine 2 cups sugar with 1 cup water, adding 1/2 teaspoon lemon juice or 1/4 teaspoon cream of tartar to speed up the reaction. Heat the solution to a low boil on the stovetop in a heavy saucepan, washing down the sides of the pan with a little additional water to dissolve any stray sugar crystals. Use a candy thermometer to monitor the temperature, which will rise above the boiling point of water as the water in it boils away. Once it reaches 230° F., remove the pan from the heat and allow the syrup to cool, then pour it into a clean jar, pop on the lid, and store in the refrigerator. Substitute invert syrup for no more than half of the sugar in your feeder solution and reduce the water slightly (by about 2 tablespoons per cup) to compensate for the water in the syrup.

Safety first! Lights and heating tape present fire and electrocution hazards. Use only products that are rated for outdoor use, including extension cords. Do not use electric heating pads outdoors! Don’t enclose Christmas lights inside a cozy or place a cozy-covered feeder too close to a heat lamp—it could start a fire. Heat lamps or Christmas lights may melt the flimsy plastic of discount-store feeders.

Useful links:

Feeding hummingbirds in winter in Indiana

Hummingbird feeder heater using Christmas lights

More on making and using invert sugar from Not So Humble Pie

Related posts:

Helping hummingbirds through winter weather

When the going gets chilly, the chilly get crafty

Helping hummingbirds through winter weather

With the usually temperate Pacific Northwest battered by fierce winter storms, there’s a lot of concern about how the resident Anna’s Hummingbirds are handling brutal temperatures and frozen feeders, and what their human hosts can do to help them survive.

One way to help is to use a slightly stronger feeder solution. Many people, myself included, have switched to a ratio of 3 parts water to 1 part sugar for all or most of the year. The sugar concentration (about 23% by weight) is closer to the average sugar content of hummingbird flower nectars (about 25%) than the standard 4:1 recipe (about 18%), and it has the advantage in winter of freezing a little more slowly.

It’s important not to go overboard, because more is not necessarily better. Sugar solutions sweeter than 3:1 can be syrupy enough to interfere with feeding efficiency, and this effect is magnified as temperatures plunge. There’s also the issue of dehydration, since nectar is a hummingbird’s main source of water (especially when everything else is frozen).

Even 3:1 will freeze if the temperatures dip low enough, but some winter hummingbird hosts have reduced the need for switching feeders by placing them next to a window (the more poorly insulated the better), inside an open shelter made of plywood, or under an outdoor-rated heat lamp.

If you make the switch to 3:1, you’ll need to adjust your expectations a bit. Since it contains more calories per drop than 4:1, your birds will not have to visit as often. It may look as though they’re avoiding the feeder when actually they’re just feeding more efficiently.

Related posts:

Keeping hummingbird feeders from freezing

When the going gets chilly, the chill get crafty

Rethinking winter hummingbirds

Keeping hummingbird feeders from freezing

Running the hummer numbers

I just ran across a post from last August on The Fat Finch Bird Brain Blog that addresses the frequently asked question about how to calculate the numbers of hummingbirds visiting your feeders. The bloggers based their formula on a book that they absolutely gush over, Hummingbirds of North America by Dan True. True is a meteorologist by profession and was the weatherman for an Amarillo, Texas TV station when my husband Tom was growing up there. Tom has fond memories of True rushing through his weathercast to have time to show his amateur wildlife films.

Nostalgia aside, I don’t share the TFFBB bloggers’ enthusiasm for True’s hummingbird book. It’s full of half-baked ideas, misinterpretations of other people’s work, and out-of-date information such as the sugar-consumption figure on which the TFFBB bloggers based their feeder-usage formula. They said they’d love to hear from anyone with different methods of estimating hummingbird populations around feeders, so I’ll share my take on the issue plus a couple of others. (Warning to math and chemistry geeks: Biology is messy business, so the measurements and calculations used below will be a bit sloppier than you might like.)

The actual statement from True’s book is: “Hummingbirds eat an amount of 25% content nectar that is equal to their body weight, daily (Skutch 1973).” The source cited is Alexander Skutch’s Life of the Hummingbird, which I no longer have in my library and so can’t check to be sure the number was cited correctly (the clumsy sentence structure suggests it’s not a direct quote). This is a pretty sweeping generalization to start with, and whoever came up with this figure miscalculated by a pretty large margin.

Studies of field metabolic rates (the average rate at which an organism consumes energy as it goes about its daily life) indicate that small hummingbirds such as Black-chinned and Ruby-throated are going to need 45% to 50% of their body weight in sucrose (a.k.a. white sugar, the dominant sugar in the nectar of hummingbird flowers) to get through an ordinary day, so they would actually need 180% to 200% of their weight in a 25% sucrose solution.

A 25% solution is much stronger than most people use in their feeders. The generally recommended proportion is 1 part table sugar to 4 parts water by volume, which comes out to about 18% sugar by weight. Converting to this recipe, it would take approximately 250% to 280% of the bird’s weight in ordinary 1:4 feeder solution to meet each bird’s daily energy requirements.

So, how do you use these data to estimate numbers of feeder visitors? The simplest way is to convert grams to fluid ounces so that you can measure the volume consumed (you can even mark your feeder and estimate usage on the fly).

According to my postal scale, one fluid ounce of 1:4 sugar water weighs about 35.5 grams (approximately 20% more than its plain water counterpart). We’ll average the weight of the birds to 3.5 grams, or about 10% of the weight of a fluid ounce. Multiply that times by 265% for average consumption and we get 0.265 fluid ounce of 1:4 feeder solution per bird per day, which we’ll round down to 1/4 fluid ounce per bird per day. This multiplies out to around 32 smallish hummingbirds per 8 ounces of 1:4 sugar water, 128 per quart, and 512 per gallon. This is higher than the TFFBBB estimate, which is not surprising considering the differences between our figures for weight and consumption rates of the birds and weight/volume ratio of the sugar solution.

Of course, there are a lot of factors that can skew this already crude estimate. The amount of sugar water each bird consumes may be greatly reduced when natural nectar sources are available and greatly increased when the birds are under stress from cold, drought, courtship, fighting, nesting, and/or migration. A given volume will supply the needs of more birds if you make your feeder solution a little stronger than 1:4, as many people (myself included) do in winter and migration, and fewer if you make it a little weaker. Size figures in as well, so a given volume of sugar water will feed fewer Anna’s than Black-chinneds.

The late William A. Calder III Stephen M. Russell, professor emeritus at the University of Arizona and the world’s authority on Rufous and Broad-tailed co-author of the Birds of North America life history account on Black-chinned Hummingbird, estimated that a gallon of sugar water would feed about 750 Black-chinneds for a day. Based on published field metabolic rates, this number would be quite high unless you are a) using a ratio of sugar to water much higher than usual for feeders (almost 28%) or b) assuming that the birds are getting a significant fraction of their calories from other sources. I wish I knew how Bill Steve arrived at this figure, but since I don’t I’ll stick with the more conservative figures I derived from the metabolic studies.

Fellow hummingbird researchers Nancy Newfield and Bob and Martha Sargent have suggested a method for estimating hummingbird numbers that has nothing to do with sugar consumption. They recommend counting the number you can see at one time and multiplying this number by six. The nice folks at Bird Watcher’s Digest used this method to estimate their population of Ruby-throateds, but they also kept track of their sugar-water usage. Based on a half gallon of feeder solution per day, I’d estimate that they’re feeding over 250 hummingbirds, not the 139 they estimated by counting and multiplying. Of course this method would never work at really busy feeders like the ones at the home of my friends Bruce and Sue in Arizona’s White Mountains (below), but it’s one more approach to a challenging question.

Sitko hummers in the White Mountains, July 2007

One additional nitpick about the TFFBBB entry: It assumes that Ruby-throated Hummingbirds migrate south across the Gulf of Mexico when the evidence strongly suggests that the majority take an overland route around the Gulf in fall migration. They didn’t get this from Dan True, whose book thoroughly documents his skepticism about trans-Gulf migration in either direction (he’s apparently unaware of the many Ruby-throateds that take refuge on offshore oil rigs and fishing boats each spring, along with other trans-Gulf migrants, or eyewitness accounts of them skimming the waves on approach to coastlines).