“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.
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
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.
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.