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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Search of the Week: “is sevin powder safe for hummingbirds”

Hummingbirds should be dusted with pollen, not pesticides.

Hummingbirds should be dusted with pollen, not pesticides.

NO! Sevin is an indiscriminate pesticide that’s considered moderately toxic to birds. Even if it doesn’t kill hummingbirds outright, it will kill their prey and deprive them of a vital food source. There are many safer and more targeted solutions available for controlling garden and household pests.

Mother Earth News: Organic Pest Control: What Works, What Doesn’t

About.com: Natural & Organic Pest Control Solutions for the Garden

Grist: A guide to non-toxic pest control

Bad news about free-roaming cats

Lucky Wilbury, our most recent shelter cat, lounging on the cat throne. We have no intention of allowing Lucky outdoors off leash, as much for his protection as for the wildlife. Our previous cat, Bart, snuck out the door one night when the coyotes were howling and Great Horned Owls hooting. He was never seen again. We feel like we let him down and only hope that he met a quick, merciful end, not like the weeks, months, or years of suffering endured by most stray and feral cats.

There’s been a recent flurry of bad news about free-roaming cats, which is timely considering a recent visit to the comments section of one LB&E post by an incipient cat hoarder. His last comment was so out of touch with reality that I did him a favor by declining to publish it. That’s tragically typical of the breed, but I hold a polyanna-ish confidence in the power of facts to overcome the disinformation thrown around by obsessive cat defenders (OCDs).

Oregon Plague: Woman Contracted Disease From Cat

Thought theBlack Death” was history? Think again. These days, plague is usually contracted from the bites of fleas in and around rodent colonies, but cats and dogs that eat infected rodents can contract and transmit the disease and/or bring home infected fleas to their human families. (Warning: The article is headed by a grisly photo of the original victim’s blackened hand.)

Rabies threat prompts town to trap feral cats

A kitten adopted from a TNR program tests positive for rabies:

The kitten was friendly and domesticated, according to the family that adopted it. Because of its demeanor, police aren’t sure that the kitten was part of the feral colony – there is a chance it was abandoned in the park. [emphasis mine]

One big reason that TNR is such a failure at reducing, much less eliminating, feral cat colonies is that the conspicuous presence of “managed” colonies in public places tends to attract people looking for places to dump unwanted pets. Inadequate commitment to vaccinating all cats in a colony at recommended intervals to prevent outbreaks of rabies, feline immunodeficiency virus, feline leukemia virus, etc. makes it a public health failure, too.

Study Finds Free-Roaming Cats Pose Threat from “Serious Public Health Diseases”

This press release from the American Bird Conservancy reports on an important new paper published in the journal Zoonoses and Public Health: “Zoonotic Diseases Associated with Free-Roaming Cats,” by R.W. Gerhold and D.A. Jessup (2012). The study reviewed the various diseases that infect free-roaming cats and the implications for public health of trying to manage feral cat populations via TNR. Three significant findings related to the second story above:

  • Free-roaming cats are disproportionately responsible for exposing humans to rabies.
  • Cat colonies “managed” by TNR attract unneutered, unvaccinated cats and increase their survivorship and reproductive success, leading to increases in colony size and potential for disease transmission.
  • Feeding stations for feral cats attract wildlife such as raccoons, skunks, and foxes that may transmit rabies and other diseases to the cats and/or carry feline diseases into the wild. (Wild predators that prey on free-roaming cats are also vulnerable to their diseases and parasites; strains of feline leukemia virus that have killed critically endangered Florida Panthers have been linked to domestic cats.)

An even more insidious public health menace related to free-roaming cats is toxoplasmosis. The organism that causes this disease can infect many animals, but cats are the only ones that pass the parasite’s infective oocysts in their feces. A cat may only shed oocysts for a couple of weeks early in the infection, but they can persist in contaminated soil—garden beds, children’s sand boxes—for years. Authors Gerhold and Jessup cited a 2011 study that found that 63 percent of the patients with acute toxoplasmosis had become infected through contact with cat feces.

One more cat item that relates to the “kitty-cam” study in Georgia:

Opinions from the Front Lines of Cat Colony Management Conflict

The authors conducted a survey of opinions about feral cats and their management with cat colony caretakers (CCCs) and bird conservation professionals (BCPs) across the United States. Naturally, they found strong polarization between the two groups (even though substantial portions of both described themselves as both cat- and bird-people), and they also documented how poorly informed/in denial CCCs were about the impacts of free-roaming cats on wildlife and public health. Even among the BCPs, awareness of feral cat issues was lower among respondents who lacked college degrees, so there’s a need for outreach and education even within the bird conservation community.

The authors suggest:

To the extent the beliefs held by CCCs are rooted in lack of knowledge and mistrust, rather than denial of directly observable phenomenon, the conservation community can manage these conflicts more productively by bringing CCCs into the process of defining data collection methods, defining study/management locations, and identifying common goals related to caring for animals… Our findings suggest that when such collaborative measures are not logistically possible, CCCs may be more likely to accept scientific results framed in terms of directly observable phenomenon (e.g., feral cats kill wild animals) rather than indirectly observable phenomenon (e.g., feral cats contribute to global declines among songbird populations). For instance, most CCCs see direct evidence of cats killing wild animals and would find denying those experiences difficult without creating some degree of cognitive dissonance.

In discussion of the Georgia “kitty-cam” study, OCDs glommed onto the low number of documented kills by the pets in the study, even though a conservative extrapolation of the results suggests that free-roaming cats kill more than 2 billion animals per year. It seems obvious that feral cats, even those that are being fed, will hunt more than well-fed, part-time outdoor pets, but seeing might be believing. It’s time to put “kitty-cams” on feral cats in managed colonies so that CCCs and OCDs can see the carnage up close and personal.

Einstein was not an entomologist

Male Squash Bee in pumpkin flower

Squash Bees are among approximately 4000 species of native bees (and thousands of other native pollinators) in North America.

If the bee disappeared off the face of the globe then man would have only four years of life left. – Albert Einstein

The quote above, as the caption to a photo of a honeybee, is making the rounds on Facebook. While I appreciate the environmental sentiment behind it, there are several serious problems:

  1. There’s no evidence that Einstein actually said or wrote this. It wouldn’t be the first time someone tried to bolster a statement’s credibility by misattributing it to a famous dead person.
  2. Even if he did, he was a physicist, not an entomologist or pollination ecologist. Being a genius in one field doesn’t make someone an instant expert in another. I’d be far more impressed if this quote was attributed to Steve Buchmann, but regrettably few people have heard of the University of Arizona’s eminent bee ecologist.
  3. “The bee” suggests that the quote refers to the honeybee (Apis mellifera), as we would understand that “the horse” refers to domestic horses and “the dog” refers to domestic dogs. There are thousands of other species of bees, and many of them are important to agriculture. North America’s native flora and indigenous agriculture got along quite well before European colonists introduced the honeybee, thank you very much.*
  4. I’m going to belabor the previous point, because I find it really annoying when people use “the [generic singular noun]” to make sweeping generalizations about large and diverse groups, e.g. saying “the hummingbird is the world’s smallest bird,” when many hummingbirds are larger than many small songbirds. AARGH!**

It’s hard to overstate the importance of pollinators, but too many people obsess over the honeybee without understanding their dark side. Yes, the decline in honeybee populations in North America is causing problems, mostly for beekeepers, the farms that use their services, and people who eat a lot of honey. From environmental and public safety perspectives, however, the decline isn’t necessarily a bad thing. As important as they are to agriculture, honeybees take food out of the mouths of native pollinators and present a real danger to people, pets, and livestock.

From most of the southern U.S. through Central and South America, the feral (“wild”) honeybee population carries genes from highly aggressive African strains that have earned them the nickname “killer bees.” Though virtually indistinguishable from pure European honeybees, Africanized bees attack en masse when they sense a threat to their hive. Even a single sting from any honeybee can be fatal to those allergic to their venom, but Africanized bees often sting their victims hundreds of times. You don’t have to be allergic to die from such an assault, and many people have. They also defend a larger area around their hives and will chase perceived predators farther than their European cousins do. Where these aggressive bees are known to occur, it’s prudent to assume that any feral honeybee hive is Africanized and give it a wide berth.

Native bees are excellent pollinators and nowhere near as dangerous to people and pets as honeybees. They already do much of the pollination work in our gardens, as long as some natural habitat remains nearby to support their nests and other ecological needs. If farmers are going to make effective use of native bees’ services, they’ll need to reduce field sizes and pesticide use and create mosaics of cultivation and native vegetation, and that’s also a good thing for thousands of other insect species plus birds, mammals, reptiles, etc. that can’t survive in our current agricultural wastelands.

References:

Bugguide.net: Native Bees of North America

Science Daily: Bees, Fruits and Money: Decline of Pollinators Will Have Severe Impact On Nature and Humankind

Science Daily: Honeybees May Not Be as Important to Pollination Services in the UK, Study Suggests

Science Daily: Native Bees Could Fill Pollinator Hole Left By Honeybees

Science Daily: Wild Pollinators Support Farm Productivity and Stabilize Yield

Montana Wildlife Gardener: Build a Mason Bee House in 5 Minutes

* Even if all bees of all species disappeared, we’d still have thousands of other pollinator species that fill similar ecological niches, including wasps and flies. Also, loss of pollinators wouldn’t directly affect crops that don’t need pollination: wheat, corn, rice, and potatoes come to mind.

** A FB commenter tried to defend the quote by claiming that the quotee was using “the bee” to refer to all pollinators(!). If so, why wouldn’t the quotee just say that explicitly? In fact, the history of the quote per Snopes.com suggests that it originated with French beekeepers, which supports the assumption that “the bee” in question is the honeybee.

“Kitty-cams” document lives of outdoor cats

Injured phoebe

An Eastern Phoebe with a mangled wing awaits death at the jaws of a pet cat.

The National Geographic Society and University of Georgia recently teamed up to apply “critter-cam” technology to understanding the lives of pet cats, documenting not only their predatory habits but the many hazards they face.

The team, led by Kerrie Anne Loyd of the University of Georgia, attached small video cameras to 60 outdoor house cats in the city of Athens, Georgia. The cats’ owners were recruited through newspaper ads and assisted the team by doing daily downloads of video from the cameras.

The most important findings were about cat predation. Loyd said:

In Athens-Clarke County, we found that about 30 percent of the sampled cats were successful in capturing and killing prey, and that those cats averaged about one kill for every 17 hours outdoors or 2.1 kills per week. It was also surprising to learn that cats only brought 23 percent of their kills back to a residence. We found that house cats will kill a wide variety of animals, including: lizards, voles, chipmunks, birds, frogs, and small snakes.

It’s no wonder so many cat owners are unaware that their pets ever kill wildlife. Even if they found every animal their cats brought home, they’d still miss more than three quarters of the death toll.

The cats in the study were outside for only 5 to 6 hours a day on average. It’s sobering to compare these well-fed pets to homeless/feral cats that are outdoors 24/7/365 and may hunt for survival as well as recreation.

Dr. George Fenwick, President of American Bird Conservancy, found the project’s findings alarming:

If we extrapolate the results of this study across the country and include feral cats, we find that cats are likely killing more than 4 billion animals per year, including at least 500 million birds. Cat predation is one of the reasons why one in three American bird species are in decline.

Think about that: 4 billion animals, including at least a half billion birds, that die purely because of human irresponsibility.

The cameras also documented risky behavior that should alarm cat lovers: crossing roads, hiding under vehicles, climbing trees, exploring roofs and storm drains, confronting dogs, opossums, and other cats, and killing small mammals that are vectors for diseases such as toxoplasmosis and Lyme disease.

The National Geographic & University of Georgia Kitty Cams Project

American Bird Conservancy: “KittyCam” Reveals High Levels of Wildlife Being Killed by Outdoor Cats

American Bird Conservancy: Cats Indoors

“Managing” feral cat colonies: kindness or cruelty?

Bart, a former stray that rules our house

At left is Bart, Prince Among Cats. Ordinarily my husband and I adopt from shelters, but Bart found us first.

He showed up in our driveway one scorching June afternoon in 2004 to scrounge from our garbage. When I arrived home and let our dog out of the car, she made a beeline for the trash cans and stuck her nose between them. A high-pitched keening rippled through the air like an audible heat wave. Pulling Josie back, I peered into the shadows to find the source of the noise: a tiny, terrified brown and white kitten.

After a brief struggle I managed to get the little guy inside, locked up Josie and our other cat, put out some water and food, and left him alone. Within 30 minutes he’d refreshed himself, taken a short tour of the kitchen and living room, and curled up to sleep atop the couch cushion behind my head. When Tom came home, he rolled his eyes at my foundling, but within 24 hours we both had abandoned any thought of sending the little stray to the shelter and an uncertain fate.

Bart will never know how lucky he is. Though still in the prime of his life, he’s already outlived the average homeless cat. He’ll never be ripped to shreds by dogs, eaten by a coyote or bobcat, shot, hung, set on fire, or skinned alive by a sadistic teenager, or crushed under the wheels of a car. He’ll never again go hungry, nor will he ever suffer from malnutrition, parasites, communicable diseases, insect or scorpion stings, snakebite, or abscessed wounds from fighting. I expect to have another eight to ten years to enjoy his company and cater to his whims. If the consequences of quantity of life diminish his quality of life beyond reasonable limits, we’ll do the responsible thing and allow our vet to put a quick, humane end to his suffering.

Millions of other cats die each year simply because there are too many pets and not enough caring, responsible homes. The lucky ones are euthanized at shelters or veterinary clinics. The unlucky may spend weeks, months or years scrounging on the streets or in the wild before dying from disease, starvation, predation, accident, or malicious acts. Thousands of self-identified cat lovers compound this cruelty by supporting programs to “manage” colonies of free-ranging homeless cats, which only prolongs these animals’ misery, jeopardizes the health of people and pets, and results in the needless deaths of neighboring wildlife.

I give most feral cat defenders the benefit of the doubt for good intentions, even though an obsession with prolonging the lives of as many cats as possible even at the cost of millions of other animals’ lives seems more like hoarding than humanitarianism. I’m equally certain that some leaders of this movement manipulate big-hearted but naive or emotionally vulnerable people into doing their dirty work: wasting their own time and money subsidizing feral cat colonies, badgering humane organizations and animal control agencies into promoting and conducting in situ feral cat “management,” agitating against cat-control ordinances, etc.

Rather than plow into the growing mountain of evidence demonstrating the damage free-roaming cats do to wildlife, their threats to human health, and the ineffectiveness of TNR (Trap-Neuter-Release, also known as Trap-Test-Vaccinate-Alter-Release) in controlling, much less eliminating, populations of feral cats, I’ll refer you to the excellent resources compiled by the American Bird Conservancy:

“Managed” Cat Colonies: The Wrong Solution to a Tragic Problem

Domestic Cat Predation on Birds and Other Wildlife

Impacts of free-ranging domestic cats (Felis catus) on birds in the United States: a review of recent research with conservation and management recommendations

Cats, Birds, & You (PDF brochure, excellent for handing out to people who let their pets roam)

There’s more on this issue at Making Tracks, the blog of The Wildlife Society.

This scientific study debunked some of the common claims of TNR advocates.

Another summary site that includes critiques of TNR-biased research studies: TNR Reality Check

I’d also like to send a National Feral Cat Day message to the ostensibly respectable “humane” organizations that support TNR:

If you really care about feral cats, the only truly humane, ethical, and environmentally responsible alternative to euthanasia is TAPPIES:  Trap, Alter, and Permanently Place In Enclosed Sanctuaries.

Salting the earth, oiling the sea

For the last few months life has been an emotional roller coaster. The weather here in southeastern Arizona has been insane. Wildlife and people alike are still hurting from last summer’s drought, despite abundant winter rains that produced a good spring wildflower show and renewed the flow of creeks and rivers. A snowstorm struck the high desert and sky islands at the end of April, during what is usually the peak of spring migration. Seeing Red-faced Warblers and hummingbird nests in the snow was an unforgettable yet heart-wrenching experience.

On the personal front, Tom and I are celebrating the engagement of one of our most cherished friends, but three other friends recently lost battles with cancer (two in one week), and three more are fighting it. Many of our friends, neighbors, and colleagues are still struggling with the effects of the economic downturn, and the picture got bleaker with Arizona’s budget crisis, radical cuts to funding for education, and a tourism boycott spurred by the passage of state legislation promoting racial profiling and banning ethnic studies.

A more distant landscape that we love and the communities that depend on it have been brutalized, perhaps beyond recovery. I’m not trying to make the Deepwater Horizon disaster about me, just saying that as a native Texan who spent many happy days on the Gulf Coast I can empathize with the maelstrom of emotions—grief, rage, helplessness, resignation—that residents of the region are feeling right now.

I have nothing but disgust for the cheerleaders for the oil industry who keep chanting “drill, baby, drill” and “jobs, jobs, jobs” in the face of this tragedy. Human lives have been lost. Millions of animals and plants, parts of a natural cornucopia of marine and estuarine ecosystems, are doomed. Traditional ways of life and the communities that depend on them have been devastated. That’s far too high a price to pay for the illusions of energy independence and economic security.

It occurred to me that the oil companies and other huge industries stand to win big from this disaster beyond a short-term spike in oil prices. With the poisoning of the Gulf’s ecosystems, thousands of residents who for generations have fed their families directly from the bounty of the coastal wetlands and the sea suddenly have no jobs, no money to buy food, few immediate alternatives, and little hope for the future. The tourism industry that struggled to recover after Hurricane Katrina was dealt another brutal blow, leaving even fewer options for small businesses and the people they employ. Families and communities will be strained to the breaking point and beyond, as they were in the aftermath of the Exxon Valdez.

Into this economic vacuum and social chaos step BP, TransOcean, Halliburton, and their ilk. Having figuratively sown the earth with salt, destroying the fertility of the Gulf and the traditional livelihoods of its people, they’ve created an employers’ paradise now and for the foreseeable future. These companies and other corporate giants will have cornered the Gulf Coast job market. It’s already started, with BP offering to hire out-of-work fishing boats for cleanup work. What’s to stop them from controlling the entire economy of coastal communities, turning once proudly independent Americans into wage slaves?

Part of me wants to see all the U.S. assets of BP, its partners Anadarko and Mitsui & Co., and its contractors TransOcean and Halliburton seized and turned over to a trust to fund ongoing cleanup of the Gulf, restoration of wildlife habitat, rehabilitation of oiled wildlife, and support of communities whose traditional economic base has been obliterated.

Of course, it would be a huge mistake to tie the welfare of the Gulf and its people to continued exploitation of offshore oil. That’s what led us to this awful situation in the first place. Think about all the people who have had so little to say about the disaster because they depend on the petroleum industry for their income. This isn’t just employees of the oil companies and/or the contractors that serve them. It’s conservationists, too.

Members of the oil and gas industry are major contributors to conservation organizations such as TNC, Conservation International, and the Sierra Club. In return for the millions they donate to these organizations, the companies get photo ops and fake awards to dress up their ads and annual reports, putting on pretty “green” masks to distract their shareholders and the general public from the damage they’re doing to the environment.

Even the promising Teaming with Wildlife proposal was hijacked by oil interests. The original bill would have emulated the highly successful Pittman-Robertson Act and Dingell-Johnson Act, establishing modest federal taxes on wildlife-related merchandise (bird feeders, field guides, camping equipment, cameras, etc.) to fund nongame conservation and watchable wildlife programs. TWW had widespread support from the public, manufacturers, and retailers, but because “tax” is a four-letter word in some circles oil-friendly members of Congress cut a deal to fund wildlife programs with revenues from offshore oil leases. Conservationists were forced to accept a Faustian bargain that is now coming back to haunt us.

Yes, the deep pockets of the oil companies are tempting, but the costs are just too high. Thankfully, there are a few politicians who understand this and are willing to take a stand against the formidable petroleum lobby. California Governor Arnold Schwarzenegger, who had previously proposed expanding offshore drilling to put desperately needed revenues into state coffers, said, “You turn on the television and see this enormous disaster, you say to yourself, ‘Why would we want to take on that kind of risk?'” (Why indeed. Perhaps President Obama would like to answer that question.) “If I have a choice to make up $100 million and what I see in Gulf of Mexico, I’d rather find a way to make up that $100 million.”

I like to think that Gov. Schwarzenegger would come to the same conclusion even if the coastlines of his state were inhabited by working people of modest means instead of rich celebrities. Here’s hoping that other governors and the President follow his example.

Crude Awakening: An infographic to help you understand the oil spill catastrophe in the Gulf of Mexico and the incredible costs that will affect us all

Integrity in Science: Non-profit Organizations Receiving Corporate Funding

Wildflowers of the Sierra Madre

GrrlScientist posted a couple of photos of cultivated dahlias in Manhattan (one so pink it hurts my eyes), so I though I’d post photos of some relatives of this and other garden ornamentals that grow wild in the Sierra Madre Occidental of western Chihuahua.

Update: Species-level IDs of Salvia townsendii and Euphorbia colorata courtesy of Wynn Anderson, Botanical Curator Emeritus at the Chihuahuan Desert Gardens of the Centennial Museum at the University of Texas at El Paso.

Something to crow about…

from an original photo by Juan Tello, licensed by Creative Commons

from an original photo by Juan Tello, licensed by Creative Commons

Woo hoo! I’ve just learned that my recent post “Do we see what bees see?” has been selected as one of 50 winners (out of >500 entries over 800 entries) for The Open Laboratory: The Best Writing on Science Blogs 2008. It’s so exciting to see Life, Birds, and Everything right up there with some big names in the science blogosphere, including some of my regular reads such as fellow bird blogger GrrlScientist. The anthology will be available shortly as both a book and a download from Lulu.com.

The illustration above (from a photo by Juan Tello, Creative Commons) serves double duty, because this year my dear husband Tom presented me with my second favorite gift of my adult life: chickens. Okay, I didn’t actually get the chickens, but Tom’s donation to Heifer International in my honor will make it possible for rural residents in Central America to receive chicks to start their own flocks. I love chickens, and Tom said maybe someday we’ll get some of our own, but in the meantime this is a gift I can feel good about and won’t have to feed and clean up after. (My favorite gift? An acre of tropical forest in Belize that Tom adopted in my honor.)

Do we see what bees see?

Trans-Pecos Morning Glory

Trans-Pecos Morning Glory

Featured in The Open Laboratory 2008!space

If you’re a hummingbird gardener, you’ve probably developed a search image that helps you select flowers most likely to please your discriminating clientele. Essentially, you’re thinking like a hummingbird, associating trumpet-shaped blossoms in “hot” colors with the promise of a sweet reward. Most hummingbird feeders are based on similar visual cues, but what if your feeder sent mixed signals that unintentionally lured less welcome critters as well as hummingbirds?

I first began to ponder this issue twenty years ago, when I was co-manager of The Nature Conservancy’s Ramsey Canyon Preserve. The preserve was having a lot of trouble with bees, mostly long-tongued bumblebees and carpenter bees, on some of its twenty-odd feeders, mostly the Perky Pet 210-P and similar models with yellow plastic “flowers” around the ports.

As I read everything I could find about hummingbirds, including pollination ecology, it dawned on me that very few hummingbird-pollinated flowers are yellow and very few bee-pollinated flowers are red. A little reading confirmed that yellow is a color ecologists associate with flowers that are insect pollinated (entomophilous, “insect-loving,” as opposed to ornithophilous, “bird-loving”). And there’s shape, too. Those five-petaled plastic pinwheels around the feeder ports could stand in for the flowers of any of hundreds of species in the sunflower family. And who pollinates those little yellow sunflowers? Bees and other six-leggity beasties, that’s who.

Since the preserve’s bookstore sold hundreds of Perky Pet feeders every year, I called the company to ask if they could make us a few red plastic flowers using the same mold as the yellow ones. A few weeks later a box arrived containing several hundred red plastic flowers. I immediately grabbed a handful and used them to replace half the yellow flowers on a couple of the problem feeders. The results were unambiguous: The bees would fly up to the red side of the feeder, buzz around, maybe land briefly, but soon take off and fly around to the other side to join their hive-mates feeding around the yellow flowers. Very few remained at the red flowers long enough to discourage hummingbirds from feeding. This continued for a couple of weeks, well beyond the time it should have taken for the bees to learn to associate the red “flowers” with food.

It was out with the yellow and in with the red on of all the preserve’s Perky Pet feeders. The leftover red flowers we handed out to preserve visitors having bee problems with similar feeders. Eventually we phased out Perky Pet feeders altogether (even in the bookstore), but until then this strategy helped to reduce the preserve’s bee problems. Disappointingly, when I reported these observations to Perky Pet and suggested that the company consider at least offering red replacement flowers, the representative’s only comment was, “Well, our customers like the yellow flowers.” Not their feathered customers, of course, but the ones with the cash.

But some people report no problems with bees on feeders with yellow parts, and others have terrible bee problems on all-red feeders. Why are some feeders with yellow parts ignored by bees? And why do some red feeders attract bees while others don’t?

The story is actually pretty complicated and starts with the different ways that bees, birds, and humans see the world. According to “Why Are So Many Bird Flowers Red?” by Miguel A. Rodríguez-Gironés and Luis Santamaría, the eyes of most bees, including honeybees, contain three types of color-detecting cone cells (trichromacy), each of which is sensitive to different wavelengths of light in a different band. The three sensitivity peaks fall at 340 nm (near-ultraviolet), 430 nm (violet-indigo), and 540 nm (yellow-green). Human eyes also contain three types of cone cells, but the peak sensitivities fall around 424 nm (indigo-violet), 530 nm (yellow-green), and 560 nm (yellow). Birds go us and bees one better with four types of cones (tetrachromacy) peaking at 370 nm (near-UV), 445 nm (indigo), 508 nm (green), and 565 nm (yellow) (Goldsmith 2006). The graphic below is my attempt to visualize the differences in color sensitivity between humans, honeybees, and hummingbirds:

Notice that none of these photoreceptors peaks in the red range (~650 nm), yet we humans (and most birds) see red reasonably well. That’s because each type of cone cell can be stimulated by wavelengths near as well as at its peak. The sensitivity declines with increasing distance from the peak wavelength, so it takes some pretty intense red light to stimulate the yellow receptors of birds and humans.

So, leaving out some evolutionary bells and whistles that may enhance avian and insect color vision, bees’ eyes are substantially less sensitive toward the red end of the spectrum than our eyes or birds’ eyes. Both Rodríguez-Gironés & Santamaría and Spaethe, Tautz, and Chittka (2001) note that bumblebees presented with red flowers have a harder time locating them. Logically it should be likewise with red vs. yellow feeder parts, but it’s not quite as simple as that.

One variable has to do with the bees’ ability to see ultraviolet light. Insect-pollinated flowers often reflect UV differently from surrounding foliage and may even have UV markings that help attract and guide their pollinators. Hummingbirds can see into the near ultraviolet, too (Goldsmith 1980), yet their flowers don’t seem to use UV cues. In a tropical study, Doug Altshuler (2003) found that hummingbird-pollinated flowers reflected light mainly in the visible red wavelengths. Altshuler concluded that:

…hummingbird-pollinated flowers are not tuned specifically to hummingbird color sensitivity but instead may decrease conspicuousness to bees and other insects that have poor visual sensitivity to long-wavelength [e.g. red] color.” [emphasis mine]

Applying this conclusion to feeders, it’s clear that differences in UV reflectance between different types of plastic could make some feeders, or feeder parts, as conspicuous to bees as a neon sign in a dark alley, regardless of how they appear to human eyes.

But it turns out that contrast is more important than color alone in helping bees find flowers. The compound eyes of insects are capable of very low image resolution. The view through even the best compound eye was compared by a 19th-century naturalist to “a picture about as good as if executed in rather coarse wool-work and viewed at a distance of a foot” (Land 1997). In modern terms, think about viewing a normal (low-def) TV screen or CRT computer monitor from about an inch away.

Spaethe and colleagues noted that bees see color less well than contrast. The further a bee is from a flower, the larger that flower needs to be for it to be able to discriminate its color. It also takes them longer to process differences in color than differences in contrast. Naturally, the most important contrast is between flowers and the surrounding green foliage, so when searching for flowers at distances of more than a few inches, bees tend to home in on objects that stimulate their yellow-green receptors significantly more or less than the background foliage. The green receptors in bees’ eyes can be stimulated by red light of sufficient intensity, but whether they perceive the difference between a red flower and its green background depends in part on the relative intensities of light reflected from each.

Color and contrast notwithstanding, a combination of opportunity and necessity may be responsible for much of the variation in bee problems at hummingbird feeders. Not only do drought, late freezes, and other factors that reduce flower availability tend to increase bee problems, but some bees may have evolved to take advantage of bird-pollinated flowers as a back-up or even primary nectar source. Raine and Chittka (2005) note that among bumblebees, the one species that showed a distinct (though secondary) preference for red is Bombus occidentalis, a species whose range in western North America is rich in hummingbird-pollinated flowers. The marauding carpenter bees (Xylocopa californica arizonensis) that rob nectar from my cultivated salvias also take advantage of the natural bounty of bright red, tubular ocotillo flowers in the late spring dry season (Scott et al. 1993). Like a naturally abundant hummingbird flower, hummingbird feeders present a rich resource for any bee capable of taking advantage of it. A poorly designed feeder is going to be more profitable for bees to exploit than a thoughtfully designed one, which is why a feeder’s vulnerability to bee problems may go beyond color.

Until we know how different hummingbird feeders appear to bees and other insects, we can’t be absolutely sure how much influence color alone has on the potential to attract unwelcome feeder visitors. Nevertheless, the scientific evidence clearly indicates that it’s wise to avoid feeders with parts that reflect light in the yellow to violet “bee-friendly” portions of the visible spectrum.

References:

Altshuler, Douglas L. 2003: Flower color, hummingbird pollination, and habitat irradiance in four neotropical forests. Biotropica 35(3):344–355. Abstract

Goldsmith, Timothy H. 2006. What Birds See. Scientific American. PDF

Goldsmith, T.H. 1980. Hummingbirds see near ultraviolet light. Science 207:786-788.

Land, Michael F. 1997. Visual acuity in insects. Annual Review of Entomology 42:147-177  PDF

Raine, Nigel E. and Lars Chittka. 2005. Colour preferences in relation to the foraging performance and fitness of the bumblebee Bombus terrestris. Uludag Bee Journal, Volume 5, Issue 4 (November 2005): pp. 145-150. PDF

Rodríguez-Gironés, Miguel A., and Luis Santamaría. 2004. Why Are So Many Bird Flowers Red? PLoS Biol. 2004 October; 2(10): e350. Link

Scott, P. E., S. L. Buchmann, and M. K. O’Rourke. 1993. Evidence for mutualism between a flower-piercing carpenter bee and ocotillo: use of pollen and nectar by nesting bees. Ecological Entomology 18:234-240.

Spaethe, J., J. Tautz, and L. Chittka. 2001. Visual constraints in foraging bumblebees: Flower size and color affect search time and flight behavior. PNAS 98(7):3898-3903. PDF

Thorp, R. W., and M. D. Shepherd. 2005. Profile: Subgenus Bombus. In Shepherd, M. D., D. M. Vaughan, and S. H. Black (Eds). Red List of Pollinator Insects of North America. CD-ROM Version 1 (May 2005). Portland, OR: The Xerces Society for Invertebrate Conservation. Link