Search of the Week: “hummingbird attack eyes”

LB&E has received an alarming number of hits this year from searches for information about hummingbirds attacking and even killing humans. Seriously, folks: Don’t we have enough fearmongering these days without spreading a new urban myth that hummingbirds kill people? Next thing you know the hysterical xenophobes are going to want to build the misbegotten border fence high enough to keep out illegal immigrant hummingbirds that want suck their underused brains out through their ears.

If a hummingbird buzzes around your face, it probably is attracted to your eyes, but not because it intends to puncture them with its needle-shaped bill (which is more like a straw than a stiletto). Many animals instinctively associate large, forward-facing eyes with predators, and hummingbirds, being both intelligent and masters of evasion, will often approach potential predators to size up the threat. If the object of interest proves to be something dangerous—a cat, an owl, a snake, a Chinese mantid—a common response is to harass the predator from a (hopefully) safe position while raising the alarm to attract other birds.

Hummingbirds are among many birds observed to gather to fend off potential predators. Mobbing, as it’s known to animal behaviorists, has been described as one of the few examples of social behavior in these acutely antisocial birds. In a 1958 article in The Condor, Stuart A. Altmann described the “spectacular” mobbing behavior of Anna’s Hummingbirds:

They flew around the owl, two or three inches from its head, facing it and making little jabbing motions in their flight… The bills of the hummingbirds seemed, in all cases, to be directed at the eyes of the owl. While circling around the owl in this manner, they called a short, repeated, high-pitched note.

Notice that feints toward the owl’s eyes were as far as it went. No actual eye-poking necessary; the mere threat of injury is usually enough to convince a potential predator to get the heck out of Dodge.

How a hummingbird is supposed to kill a person is beyond my imagination, other than flying into a car and distracting the driver or some such accident. Is it a case of confusion with an insect, like the rare but persistent myth that hummingbirds live only one day? (They’re thinking of adult mayflies.) Would someone who’s heard such a rumor please leave a comment with the specifics?

Related posts on this topic:

Killer hummingbirds?
Fawn-breasted Brilliants in combat

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Quote of the Day

“When you see a hummingbird for the first time, you are knocked out. It’s extraordinary. But when you see it for the second time, you are beginning to understand more about the way a hummingbird works. And as you go through and see it year after year, you learn more. It’s neverending. If I got to the situation where I said, ‘Oh, it is a hummingbird, ha, yet again,’ I would pack it in.” — Sir David Attenborough

“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.

Search of the Week: “why don’t hummingbirds get diabetes”

A male Broad-billed Hummingbird threatens an intruder in his feeding territory.

A male Broad-billed Hummingbird threatens an intruder in his feeding territory.

This week’s featured search topic has been addressed on LB&E previously here and here.

Type 2 diabetes, the disease people are thinking of when they ask such questions (because they’ve been told, wrongly,*⇓ that sugar consumption causes diabetes), is largely a modern human affliction. We eat too much, including highly processed foods full of easily digested simple carbohydrates that flood our bloodstreams with glucose. We exercise too little, contributing to getting fat and staying fat. Our bodies may continue producing insulin to aid in utilization of the glucose in our systems, but over time our cells may stop responding to it.

These issues weren’t much of a problem for our pre-industrial ancestors (even those with a genetic predisposition to diabetes), and they’re still not much of a problem for people living labor-intensive lifestyles and eating traditional diets high in complex carbs, fiber, and other good things.

They’re also not a problem for hummingbirds. More than 40 million years of evolution have adapted these tiny, hyperactive dynamos to a sugar-rich diet. To maintain some of the highest metabolic rates ever measured, hummingbirds must take in enormous amounts of energy. The most energy-dense food available to them is flower nectar. Without it, the tiny, hovering jewels we know and love would never have evolved.

You might say that hummingbirds show three classic symptoms of diabetes: they eat a lot (polyphagia), drink a lot (polydipsia), and pee a lot (polyuria). Of course, these “symptoms” are simply consequences of a high metabolism and water-rich diet. They also have very high blood glucose levels, high enough to cause serious complications in humans, but their absorption and utilization of the sugars in their diet are so efficient that almost none ends up in their urine (as it does in human diabetes patients).

Medical researchers would love to know exactly how hummingbirds avoid the short-term and long-term complications of high blood glucose, but it’s clear that their ability to do so has been honed by natural selection. Any hummingbird that had a serious defect in its ability to absorb and/or metabolize sugar would be dead within days, weeded out of the gene pool.

Here’s an in-depth examination of the issues from the perspective of human health:

Adipose energy stores, physical work, and the metabolic syndrome: lessons from hummingbirds

* Since this post was written, new research has persuaded many members of the medical community that there’s a more direct link between sugar consumption and Type 2 diabetes than decades of propaganda by Big Sugar would have us believe.

Feeder Solution Evolution Part I: The basics

The posts lately have been hummingbird heavy, but you can blame the time of year. Both southbound migrants and a few remaining locals—Rufous, Broad-tailed, Black-chinned, Anna’s, Broad-billed, an occasional Calliope, Costa’s, or Violet-crowned, and our yard’s first Lucifer—have been shrieking and jousting outside my living room window every daylight hour, so it’s hard to think about anything else (which makes it hard to get any real work done but also keeps my mind off things I’d rather not dwell on).

This is going to be a heavy post, so I’m dividing it into three parts. If all you’re interested in is what you should/shouldn’t put in your hummingbird feeder, you needn’t read any further than the end of this installment. If you’re curious about how these recommendations came about—the science and history behind them—I hope you’ll come back or click through to read the second and third installments.

Let’s kick things off with something happy. Happy, happy, happy. No stress, no angst.

A young White-eared Hummingbird drowses in the sun

A young White-eared Hummingbird drowses in the sun.

Okay, down to business. At the request of my friend and colleague Laura Erickson, who writes and edits for the Cornell Laboratory of Ornithology, I’m finally tackling this long-neglected and often controversial topic. Here is what you need to fill your hummingbird feeder:

1. White sugar.

  • Sucrose (a.k.a. white table sugar) is the main sugar in the sap of plants and also in the nectar of hummingbird-pollinated flowers (1). We squeeze sugar cane and sugar beets to get our sucrose, and hummingbirds drink nectar, sap, and properly made feeder solutions to get theirs. It does not give them diabetes. It will not rot their teeth.
  • If ordinary granulated sugar doesn’t dissolve fast enough for you, and you don’t mind trading cost for convenience, buy superfine baker’s or caster sugar instead (but not powdered sugar, which contains anti-caking agents).
  • Though pure cane sugar is often recommended over pure beet or blended sugar (which is usually labeled simply as “sugar”) based on the perception that it tastes better to the birds, it takes sophisticated testing for food scientists to distinguish between them. Sugar cane yields somewhat more sugar per acre than sugar beets but uses much more water, displaces more biodiversity, and has to be transported farther (at least in U.S. markets), so beet sugar may be the “greener” choice.

2. Good-quality water.

  • If there’s any reason that you don’t personally drink your tap water (too many minerals, has a funky taste or smell, tested positive for pollutants, etc.), don’t make your hummingbird guests drink it, either. If it’s discolored by iron, you definitely shouldn’t use it to make feeder solution (see the second bullet point under the “don’ts” below).
  • Researchers have determined that hummingbirds’ kidneys are incredibly good at getting rid of water without losing their bodies’ electrolyte salts (2), which clears the way for feeder solutions made with water purified by reverse osmosis or distillation. Water softened by ion exchange is high in sodium, and overloading the birds on sodium may not be a good idea.

Sugar. Water. That’s all you need. Really.

The list of things you should not put in your hummingbird feeder is a wee bit longer:

  • Honey. It’s a natural food, but only if you’re a honeybee. Bees start with the nectar of flowers not typically used by hummingbirds, modify it with digestive enzymes, then barf it back out and evaporate off most of the water. The final product contains less palatable sugars plus stuff you seriously don’t want to feed to hummingbirds. Once diluted to feeder strength, honey becomes an ideal food for a variety of microbes, including some that can cause disease. Honey-water diets have been linked with fatal yeast infections (candidiasis) in captive hummingbirds (3), and similar infections have been reported in wild ones. Honey belongs on your biscuits, not in your feeders.
  • Brown or even brownish sugar. The color derives in part from iron, for which nectarivorous and frugivorous birds have a very low tolerance (4,5). Even a little extra iron over time can build up to lethal levels in the birds’ bodies. Refined white sugar has had the trace iron removed to make it a more attractive product, which incidentally makes it safer for hummingbirds. Unfortunately for those of us who try to shop green, organic sugar is typically not fully refined to pure sucrose, so it’s not safe. Rumors of problems at tropical feeding stations may be related to the use of lightly refined turbinado (“raw”) sugar containing iron, but these reports have yet to be substantiated.
  • Artificial coloring. The vast majority of hummingbird flowers put the color on the outside, not in the nectar. FD&C Red #40 and #3, the dyes used in most “instant nectar” products and the food coloring in your pantry, are like nothing the birds would ever encounter in nature. They may not be dangerous at human consumption levels, but hummingbirds can drink more than 5 times their weight in liquid in a day. Medical research has linked large dosages of these dyes to a number of serious health problems. Backyard comparisons also suggest that the birds don’t like the way these dyes taste. If colorless sugar water just doesn’t look right to you, use a few drops of fruit juice concentrate to tint it.
  • Artificial and non-nutritive sweeteners. This includes saccharin (Sweet’N Low®), aspartame (Equal®, NutraSweet®), sucralose (Splenda®), stevia (Truvia®, PureVia®), monkfruit or lo han (Nectresse®), acesulfame potassium (acesulfame-K), erythritol, and xylitol. Hummingbirds need the calories. If they get fat, it’s for a good reason, and they won’t stay that way for long (unlike us big sluggish primates.)
  • Commercial “instant nectar” and “hummingbird food” products. Most contain unnatural additives such as dyes, preservatives, and/or flavors that, despite what manufacturers and retailers may claim or imply, have never been tested or approved as safe for hummingbirds. Those products without additives are basically overpriced boxes of extrafine white sugar (see the second bullet point under “White Sugar” above).
  • Nutritional supplements. The nectar of hummingbird flowers is little more than sugar water anyway (1), and anything else you add can cause premature spoilage and other problems. This includes commercial diets for captive hummingbirds, protein powder, fruit juice (except a few drops of concentrate to add a little color), Jell-O, Gatorade, Mountain Dew, vanilla extract, and strawberry daiquiri mix. Hummingbirds are really efficient hunters, even in winter, but if you want to supplement their protein/vitamin intake, raise fruit flies in jars or start a compost pile. For minerals during nesting season, offer clean ashes from natural wood (no synthetic logs, paper, trash, etc.).

See this post for a more comprehensive list.

Now that we have the two ingredients, the next step is determining what proportion to mix them in. Though opinions about feeder solutions vary slightly within the hummingbird community, most hummingbird experts still endorse this recipe:

4 parts water

1 part sugar

Good old 4:1 has proven itself safe and effective over more than four decades of use, it’s well within the range of sugar concentrations found in the nectar of hummingbird pollinated flowers (1), and, like a one-size-fits-most garment, it leaves enough “wiggle room” to accommodate some challenging environmental conditions without short-changing the birds on either energy or water. Hardcore hummingbird fanatics may have sound reasons for using slightly stronger or weaker solutions, but all the average hummingbird host needs to remember is 4 parts clean water + 1 part white sugar.

Stay tuned for part II, the science behind hummingbird feeder solutions.

Resources for this post:

1. Nicolson, S. W. and P. A. Fleming. 2003. Nectar as food for birds: the physiological consequences of drinking dilute sugar solutions. Plant Systematics and Evolution 238(1-4):139-153.

2. Lotz, Chris N. and Carlos Martínez del Rio. 2004. The ability of rufous hummingbirds Selasphorus rufus to dilute and concentrate urine. Journal of Avian Biology 35(1):54–62.

3. Orr, K.A. and M. E. Fowler. 2001. 18: Order Trochiliformes (Hummingbirds). In Biology, Medicine, and Surgery of South American Wild Animals, Murray E. Fowler, Zalmir S. Cubas Eds. Iowa State University Press, Ames, Iowa.

4. Frederick, H., Dierenfeld, E., Irlbeck, N., and S. Dial. 2003. Analysis of nectar replacement products and a case of iron toxicosis in hummingbirds. In Ward, A., Brooks, M., Maslanka, M., Eds. Proceedings of the Fifth Conference on Zoo and Wildlife Nutrition, AZA Nutrition Advisory Group, Minneapolis, MN.

5. Ketz-Riley, C.J. and C. Sanchez. 2015. Chapter 26: Trochiliformes (Hummingbirds). Pp. 209-213 in Fowler’s Zoo and Wild Animal Medicine, Volume 8, R.E. Miller, M.E. Fowler eds. Elsevier (Saunders).

Related posts:

Search of the Week: “if refined sugar is so bad for us, then why do we feed it to hummingbirds?”

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

Beet juice in hummingbird feeders? NO!

Search of the Week: “can I give hummingbirds mountain dew”

Geography tutor needed, apply at London (Ontario) Free Press

From “Hurricane relocates hummingbird”:

Probably the most interesting bird spotted in Nova Scotia after the passage of hurricane Earl, was a Calliope hummingbird from the American western mountains, where they are uncommon at best…

How the southwestern hummingbird ended up in Nova Scotia, is a mystery. It might have been migrating south to its wintering grounds in north west Mexico when it got caught up in Earl’s vortex.

Or not.

A couple of minor problems with this scenario:

  • Hurricane Earl never got within 1000 miles of the Calliope Hummingbird’s normal migration routes to its wintering grounds in southwestern Mexico.
  • Any Calliope Hummingbird sucked up by one of those rare Rocky Mountain hurricanes would not survive to be dropped off 2000 miles away in Nova Scotia unless the winds also transported a bunch of uprooted nectar plants and/or hummingbird feeders along with farmhouses, livestock, runaway schoolgirls, and psycho dog-hating neighbor ladies on bicycles. Oh, wait… that’s tornadoes.

Hurricanes almost certainly do “relocate” hummingbirds on occasion. If this was such an occasion and not just a coincidence, the most logical scenario is that the bird had already migrated to the Atlantic Coast before it “got caught up in Earl’s vortex.” Still highly unlikely because of problem #2 above.

Of course, fall migration is a normal time to find “wayward” birds almost everywhere in North America, even in the absence of hurricanes (or tornadoes). Calliope Hummingbirds are Canadian birds, too, nesting in British Columbia and southwestern Alberta, so this one could have traveled east-southeast completely under its own power, never coming anywhere near Earl’s path until it arrived in Nova Scotia nor even straying out of Canadian airspace.

Rant over. Please resume your normal activities.