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.

Advertisements

“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