Killer hummingbirds revisited

sherlock-holmes

“It’s a photo of a dead hummingbird! What do you make of it Holmes?”
“Impossible to say without additional evidence, Watson.”

Periodically over the nearly nine years since the publication of Killer hummingbirds?, I’ve received comments from people taking issue with what they believe that post says. Typically, these readers have witnessed an attack by one or more hummingbirds on another and wish to inform me that I’m wrong to say that hummingbirds never kill each other. The first problem is that I didn’t say “never,” and they would know this had they read as far as the bold black text in the middle of the post:

 “Only birds weakened by hunger, disease, or injuries… are vulnerable to injury and, in rare instances, death from other hummingbirds…”

Some of the reports clearly fit the qualification above, because, to quote more of the original post:

a healthy hummingbird will either defend itself or flee before a more aggressive individual gets the chance to do any significant damage.

Others provide few if any useful details of the event, even when prompted, and still others are just accounts of finding a dead hummingbird and assuming, because they had previously observed combat, that it was a case of trochilicide.

This brings us to the other problem with these reports, which is that they are never accompanied by any objective evidence—photos or video—that would support their accounts of the events (much like reports of yellow hummingbirds). A recent correspondent claimed to have seen a Black-chinned Hummingbird…

“…physically stick his bill deeply into another h.bird’s belly, twice! Then 2 more times into the back of the others neck.”

There are a couple of problems with this description as evidence of hummingbirds fighting to the death, even if one combatant is severely disadvantaged. The first is that poking is rather common in hummingbird combat, and the disappearance of the tip of an aggressor’s bill into the thick plumage of the “victim” would be understandably alarming to someone unfamiliar with hummingbird anatomy.

BCHU-bouf-brain

A hummingbird poking another’s body with its bill is a bit like someone poking Marie Antoinette in the bouffant with a knitting needle.

The second is that, even when the bill passes completely through the feathers and makes contact with the other bird’s body, hummingbird anatomy makes a fatal penetrating wound highly unlikely except in freak circumstances (see page 23 of A Field Guide to Hummingbirds of North America for an example).

This X-ray CT image of a Ruby-throated Hummingbird, showing its huge, deeply muscled rib cage, short skin-and-bones neck, and virtually nonexistent “belly,” demonstrates why hummingbirds are not as vulnerable to penetrating wounds as humans are (or as capable of inflicting them):

CT scan of a Ruby-throated Hummingbird. Copyright Digimorph.org

CT scan of a Ruby-throated Hummingbird. Copyright Digimorph.org

The issue of hummingbirds injuring one another in combat took a fascinating twist in 2014, when Alejandro Rico-Guevara of the University of Connecticut and and Marcelo Araya-Salas of New Mexico State University announced their discovery that the unusual bill shapes of adult male Long-billed Hermits make them more effective at inflicting potentially painful puncture wounds than the bills of females and juvenile males, and that males with longer, pointier bill tips were more successful at defending territories.

These revelations were newsworthy precisely because the bill shapes of the vast majority of hummingbird species, including all of the familiar North American species, show no such adaptations and confer no apparent advantages in combat. It’s also noteworthy that while the researchers observed male Long-billed Hermits poking each other during combat, they did not mention observing any serious injuries, much less fatal ones, resulting from these interactions. In fact, most of the “fighting” shown in their video consists of belligerent posturing and vocalizing with little physical contact, similar to the combat behavior of most North American hummingbirds:

(Note that the black-and-white segment depicts two non-hermit species, and the last sequence depicts courtship and mating, not fighting.)

So now we have compelling evidence that males of at least one hummingbird species have bills adapted for use as “stabbing” weapons, yet documentation of fatal encounters between healthy, normal hummingbirds is still almost as elusive as Bigfoot. I expect it will remain so, but I’m open to persuasive evidence.
Decreux LikenessesResources:

Rico-Guevara, Alejandro, and Marcelo Araya-Salasb , 2014. Bills as daggers? A test for sexually dimorphic weapons in a lekking hummingbird. Behavioral Ecology 26(1): 21-29.

Digimorph.org: Archilochus colubris, Ruby-throated Hummingbird by Dr. Ronald Stearman, The University of Texas at Austin.

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“Chemical-free” sugar?

My reply to the following e-mail bounced, so I’ll answer it here:

I’ve read the first part of your article on hummingbirds about what  to make when you feed them.

Before reading the article, I just made hummingbird food with organic sugar. I am concerned about the addictive and other chemicals in white sugar. Is there any white sugar available on the market that does not contain chemicals?  or a way to transform organic sugar in white?

Thank you for your time.

In the strictest sense, there is no product of any kind on the market that doesn’t contain chemicals. I’ll need to know what specific substances you’re concerned about (other than iron) before I can answer your question, but the way it’s phrased suggests that you may have fallen victim to fear-mongering hyperbole about white sugar. In that case, this post may be helpful:

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

One feederful of organic sugar isn’t going to kill hummingbirds because the iron concentration is very low. It’s chronic exposure to excess iron over weeks, months, or years that may cause illness and death. Unfortunately, there is no simple home remedy for removing the residual iron from organic/”raw”/turbinado sugar.

Review: Feeder Fresh Nectar Defender

(Originally submitted at Duncraft, which I do not patronize because it sells various overpriced “nectar” products that contain artificial dyes, preservatives, and/or other potentially harmful additives that don’t belong in hummingbird feeders.)

A bad idea

1out of 5

The active ingredient in this product is reportedly copper, which is an essential micro-nutrient at natural (low) intake levels and a potentially toxic heavy metal at higher doses. The fact that copper accumulates in birds’ bodies combined with hummingbirds’ extreme appetites increases the risk that the copper in this product will accumulate over time to levels that may cause scientifically documented problems such as behavioral changes, developmental abnormalities, reduced egg production and nestling survival, etc. That’s a pretty high price to pay for reducing feeder maintenance.

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: “can hummingbirds survive 100 degree heat?”

Costa's Hummingbird

Costa’s Hummingbirds are true desert dwellers, but all North American hummingbirds can tolerate summer heat if they have plenty of water.

Yes. They’ve been doing it for millions of years. As long as they’ve got shelter from the sun and plenty of water for evaporative cooling, they should be fine.

Hummingbirds will drink plain water when conditions are particularly hot and dry and/or nectar is hard to come by, but the usual sources of water pose risks of disease transmission from other birds, poisoning from rain or irrigation runoff contaminated with pesticides, weed killers, oil, antifreeze, etc. It’s safer to put out a separate feeder filled with plain water or change the sugar-to-water ratio of your feeder solution.

When the daytime highs start creeping into the 90s F., I reduce the concentration of my solution to 1 part sugar to 4 parts water. When temperatures rise to over 100° F. (which they don’t very often here in the high desert), I back off to 1:5. In parts of the Southwest where temperatures are topping 110° F., a 1:6 ratio would be advisable. Weaker solutions tend to spoil faster, but on the plus side they also tend to be less attractive to bees.

Providing water for the outside of the bird is another way to help beat the heat. I added a mister to our drip irrigation system that runs for a few minutes a day, spraying into the foliage over my hummingbird garden. It’s used year round but is especially appreciated in summer, helping to keep the birds cool and their insulating plumage in top condition.

I hate to end on a down note, but the hard fact is that every organism on Earth is going to have to adapt to rising average temperatures and greater extremes, and those that aren’t well suited to withstand “the new normal” just won’t survive.

Reference:

Hiebert, S.M. and W.A. Calder III. 1986. The osmoregulatory consequences of nectarivory and frugivory in hummingbirds and other species. Proc. XIX Internat. Ornith. Cong ., Ottawa, Canada.

Related post:

Feeder Solution Evolution Part I: The basics

“Dawn swift” illuminates origins of swifts and hummingbirds

dawnswiftFrom the spectacular Green River Formation of Wyoming comes a tiny fossil that researchers have identified as a possible relative of both hummingbirds and swifts.

When Eocypselus rowei, whose genus name is Greek for “dawn swift,” died approximately 50 million years ago, it fell into shallow, oxygen-poor water and was covered with fine layers of mud that preserved minute details of its body and plumage. Except for its long wings, the fossil shows few hummingbird-like characteristics. Its stubby bill is more like those of swifts and suggests that, like them, it fed on flying insects. Though about the length of a Magnificent Hummingbird (12 cm, 4 3/4″), its short bill, proportionally larger skull, and longer wing and leg bones would have made it heavier. “Shadows” in the stone surrounding its bones are fossilized pigment structures that would likely have given it a glossy, possibly iridescent black color like many modern swifts.

Though hummingbird fossils have been found so far only in Europe, Eocypselus shows that possible distant hummingbird ancestors did occur in the Americas.

Read the full text of the article here:

Fossil evidence of wing shape in a stem relative of swifts and hummingbirds (Aves, Pan-Apodiformes)

Read more at:

ScienceDaily

AAAS Science Now

Science 2.0

Talking hummingbirds on Arizona Illustrated

I recently appeared on the public television news magazine Arizona Illustrated to talk about hummingbirds and the Southeastern Arizona Bird Observatory‘s field studies on them. Watch the interview here:

Arizona Illustrated: Hummingbirds Among Us

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.

I get mail

I get a lot of mail this time of year asking for help with hummingbird identification. Those that are accompanied by photos are usually pretty easy to deal with, but ones like this give me a bad, bad feeling:

I live in Michigan. My daughter had a friend that lived along the Maple river. They saw yellow, red and green hummingbirds. These were brightly colored. She discribed the yellow one as looking like a goldfinch. They all appeared to be the same type of birds only different bright colors.

My sister just this week saw one that was a solid bright sky blue.

I’ve never heard of hummingbirds that have this coloring.

That’s because there aren’t any. A red and green hummingbird in Michigan is almost certainly a male Ruby-throated, but there are no yellow or solid sky blue hummingbirds among the world’s 340-odd species. None. Anywhere. However, those bright colors are found in many tiny songbirds, including warblers, buntings, and yes, finches. I shared this information, suggesting a couple of field guides and Web sites, and received this reply:

You answered my question as far as these being known.  They were definitely hummingbirds.  they were to small for anything else and the yellow, red and green variety were eating from the feeder.  my daughters friend had hit one on the yellow ones with his car and killed it.  Do you have any suggestions on how to attract them so I can get a picture

Oh, they were small? and eating from a feeder? and one was dead? Well, that’s certainly compelling evidence for not one but two previously unknown hummingbird species in the unexplored wilds of Michigan. Can’t wait to see those pictures.

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.