Time to finish one of those long-running series of Tet Zoo articles: at last, the long-awaited, much anticipated third and final instalment in the series on the clubs, spurs, spikes and claws present on the hands of numerous neornithine bird species. If you haven't done so already, do check out the previous parts here (on hand claws in general, and carpal spurs and knobs in waterfowl) and here (on carpal spurs in charadriiforms).
Those previous instalments looked at claws (widely present in modern birds: far from unique to the Hoatzin Opisthocomus hoazin) and at keratin-sheathed bony knobs and spurs. All very neat I'm sure you'll agree, but arguably less amazing than the structures I'm going to be discussing here: CLUBS. [Image above shows, at left, Pezophaps solitarius, by Frederick William Frohawk, and Xenicibis xympithecus, by Nick Longrich].
As we'll see, birds of (at least) two very distinct neornithine lineages evolved bony clubs on their hands, and in both cases these seem to have been used in (probably intraspecific) combat.
The claws, spurs and other carpometacarpal structures discussed in these articles are, ordinarily, hardly ever mentioned in the literature. But the structures present in one recently extinct bird are, in contrast, mentioned just about every single time this species is discussed, and I'd even go as far as saying that their presence is "well known". I'm of course referring to the Solitaire Pezophaps solitarius, a giant, recently extinct pigeon from Rodriguez (its anthropogenic extinction occurred some time between the 1730s and 1760s). Huge, rounded bony calluses - said by Newton & Newton (1868) to be "out of all proportion to anything of the kind yet known in ornithology" (p. 342) - are present on the proximal end of the male carpometacarpus, and appear to be hypertrophied extensor processes. These structures have a very rugose texture and would have been covered in life by horn [the adjacent diagram shown here is from Rand (1954); the annotated photo below was taken at the University of Museum of Zoology, Cambridge, UK].
The Huguenot refugee FranÃ§ois Legaut, who famously observed these birds in life, described the presence of a rounded mass "as big as a musket ball" near the end of the wing. He even said that the birds whirred their wings in display, clapped them "like a rattle" against their sides, and used them in striking enemies. In many of the larger Solitaire specimens examined by Newton & Newton (1868), both the radius and ulna had fractured and healed in life, so it seems like a reasonable deduction to conclude that Solitaires fought with their wings, as do many other pigeons. A swelling is also present on the distal end of the Solitaire radius, so this region was likely covered in horn and/or calloused skin as well. These unusual features were unique to males so are assumed to have been used in male-male combat. Male Solitaires were substantially larger than females: with estimated masses of, respectively, 28 and 17 kg, a female would only be about 60% the mass of a large male (Livezey 1993). This is the largest reported case of sexual dimorphism in neognath birds (it's exceeded by the dimorphism seen in moa, but they ain't neognaths) [UPDATE: nope. Muscovy ducks, capercaillies and Great bustards all exhibit dimorphism that exceeds what's seen in the Solitaire. See comments. Another reminder not to believe everything you read, even when it does come from an authoritative source].
Pigeons in general fight by striking each other with their wings, so it seems that this behaviour was likely inherited from the Solitaire's volant ancestors. In phylogenies, Pezophaps is close to Caloenas (Nicobar pigeons), Goura (crowned pigeons) and Didunculus (tooth-billed pigeons) (Shapiro et al. 2002). At least some of these living relatives of the Solitaire raise one or both of their wings when acting aggressively (Goodwin 1967). Here's where things become more interesting...
There's more than one large, terrestrial, knob-winged pigeon!
Having mentioned Didunculus, I've always been curious about the fact that some old sources (e.g., Rand 1954) refer to this pigeon - generally known as the Samoan tooth-billed pigeon* - as the Knob-winged pigeon. The idea that this close relative of dodos and solitaires might have enlarged bony knobs on its carpometacarpi is very interesting, but illustrations of its carpometacarpus (see the one shown below, from Worthy & Wragg (2008) [scale bar = 10 mm]) don't show any unusual structures compared to other pigeons: the extensor processes in particular looks pretty average (certainly compared to that of Pezophaps). Livezey (1993, p. 275), however, noted in passing that the extensor processes of Didunculus are overlain by a cornified integument: yet another reminder (as if it were needed) that structures present in life aren't always obvious from the underlying osteology.
* There's only one living species (D. strigirostris) and it's found on Samoa. Fossils show that it once lived on Fiji, and an extinct species (D. placopedetes) is known from Tonga. Didunculus is thus a 'pseudo-endemic' of Samoa (Steadman 2006).
Things get better when we look at other members of this 'Caloenas group' of pigeons, however. Both Goura (the crowned pigeons) and the recent extinct Fijian form Natunaornis gigoura (the Viti Levu giant pigeon, sometimes jokingly referred to the Fijian dodo) have inflated, bulbous extensor processes, with those of Natunaornis being especially big (Worthy 2001). In fact, I'd go so far as to say that the inflated extensor processes of Goura and Natunaornis look like 'prototype' versions of the enormous ones present in Pezophaps. This wasn't lost on Trevor Worthy, who wrote that "A similar development of the metacarpal process in Didunculus (Livezey 1993) and in Goura (data herein) is suggestive that these taxa shared with Natunaornis the use of their wings in combative behaviour" (p. 780). [There are very few life restorations of Natunaornis. The one on the stamp, shown below, errs in making the bird's bill too gracile: it seems that it was actually deep and robust, as shown in my speculative picture shown at left. This reconstruction has been used on Tet Zoo before]. Incidentally, there's no evidence that the Dodo Raphus cucullatus had wing knobs or clubs, though the suggestion has been made (by Richard Owen) that the wings were used in fighting.
A few other birds not mentioned here or in the previous articles might also have cornified knobs on their hands. Rand (1954) mentioned such structures in Megapodius megapodes and some thrushes, but I've been unable to find more information and haven't (yet) read any more about these possible occurrences (on the thrushes... I don't suppose it's possible that someone confused the flightless pigeon called the Solitaire with the American thrushes - Cichlopsis, Entomodestes and Myadestes - called solitaires?). Andrews (1901) made the interesting suggestion that roughened areas on the extensor process of Phorusrhacos indicated the presence of a spur or horny knob on this part of the hand. That's entirely plausible, though note that it's nothing to do with those suggestions of giant hand claws previously mooted for some phorusrhacids.
Note that the knobs that we're talking about here are quite similar to the previously discussed knobs present on steamer ducks and some other waterfowl.
Ninja ibis from Jamaica
We finish it all by looking at another extinct bird that also possessed distinctive wing armament: I'm referring to the flightless ibis Xenicibis xympithecus from Jamaica, sometimes called the Club-winged ibis. I started writing the article you're reading now in July 2010 and had no idea at all that a paper describing the club-winged condition of Xenicibis in definitive fashion was in the works (though I was familiar with this research, having heard about it all off Nick Longrich some years ago). Yes, as you'll likely now know, Nick Longrich and Storrs Olson published their description and interpretation of this remarkable bird's wings in January of this year (to date, only the online version is out). The paper (Longrich & Olson 2011) got a lot of press coverage. I was even asked to do a radio interview on it (after all, I did play a crucial role in the research [massive joke]). It was pretty weird as the radio host asked me to describe what kind of 'dino' Xenicibis was. I proceeded to explain what ibises were and how they were actually pretty familiar birds. Anyway...
Xenicibis and its incredible flail-like wings have in fact gotten so much coverage online (in the blogosphere and elsewhere (honourable mention of Ed Yong)) that there isn't much I can say that you won't already have heard before. The carpometacarpus is massive, long, curved and equipped with thick bone walls. The radius is unusually robust compared to that of most birds, while the wrist and elbow were fully mobile.
The weird wing bones of this bird have resulted in previous suggestions that it was possibly quadrupedal and that it used its hands as props, like crutches (I used to have a cartoon depicting this idea but can't find it anymore. UPDATE: FOUND IT!). I've also heard informal (and very much unpublished) suggestions that these clubs were used for bashing snakes. As Longrich & Olson (2011) argue, the wing structure seen in Xenicibis indicates that it used these limbs as flail-like combative organs, probably against other members of its own species. However, because it lived alongside various snakes, raptors and other predators it's certainly plausible that these bizarre wings were also used to fight off or even kill such animals. And good evidence for use of the wings in combat comes from healed fractures in the upper arm and hand.
Many people who regularly get close to, or handle, birds know that (as we've discussed on Tet Zoo quite a bit before) they're frequently pretty formidable animals for their size. Angry waterfowl, chickens, raptors and gulls can be real nasty: powerful and gutsy enough to fight off and injure (even kill) mammals bigger than they are. Should you encounter a specialised, weapon-bearing bird of any sort (either here or in the past, should you go time travelling) my advice is to be very, very careful and to try not to piss it off. Should you be attacked, be sure that someone is taking photos - - - that kind of stuff is blogging gold!!!
For previous articles on manual weaponry in birds, and on avian hands in general, see...
- Raven, the claw-handed bird, last of the phorusrhacids
- Attack of the flying steamer ducks
- Yes, it was a kiwi
- Dissecting an emu
- Dissecting Ozbert the ostrich
- Detachable wing-daggers. Amazing waterfowl facts part III
- Clubs, spurs, spikes and claws on the hands of birds (part I)
- Spurs and blades on the wings of jacanas, lapwings, sheathbills and archaeotrogonids (clubs, spurs, spikes and claws part II)
And for more on pigeons, big or otherwise, see...
PS - YES... at last, this short series is complete. Now to do like it says here, and kill the others too...
Refs - -
Andrews, C. W. 1901. On the extinct birds of Patagonia-I: The skull and skeleton of Phororhacos inflatus Ameghino. Transactions of the Zoological Society of London 15, 55-86.
Goodwin, D. 1967. Pigeons and Doves of the World. British Museum (Natural History) (London).
Livezey, B. C. 1993. An ecomorphological review of the dodo (Raphus cucullatus) and solitaire (Pezophaps solitaria), flightless Columbiformes of the Mascarene Islands. Journal of Zoology 230, 247-292.
Longrich NR, & Olson SL (2011). The bizarre wing of the Jamaican flightless ibis Xenicibis xympithecus: a unique vertebrate adaptation. Proceedings. Biological sciences / The Royal Society PMID: 21208965
Newton, A. & Newton, E. 1868. On the osteology of the Solitaire or Didine bird of the Island of Rodriguez. Proceedings of the Royal Society 103, 428-433.
Rand, A. L. 1954. On the spurs on birds' wings. The Wilson Bulletin 66, 127-134.
Shapiro, B., Sibthorpe, D., Rambaut, A., Austin, J., Wragg, G. M., Bininda-Emonds, O. R. P., Lee, P. L. M. & Cooper, A. 2002. Flight of the dodo. Science 295, 1683.
Steadman, D. W. 2006. An extinct species of tooth-billed pigeon (Didunculus) from the Kingdom of Tonga, and the concept of endemism in insular landbirds. Journal of Zoology 268, 233-241.
Worthy, T. H. 2001. A giant flightless pigeon gen. et sp. nov. and a new species of Ducula (Aves: Columbidae), from Quaternary deposits in Fiji. Journal of The Royal Society of New Zealand 31, 763-794.
- . & Wragg, G. M. 2008. A new genus and species of pigeon (Aves: Columbidae) from Henderson Island, Pitcairn Group. Terra Australis 29, 419-510.
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Another wonderful article - thanks Darren. What is holding up the 2nd pterosaur sex life article? I once saw a dove trying to defend its nest against a mamba in Mozambique - it failed and the chick was swallowed, but it fetched some loud smacks against the snake with its wings, even knocking its head off the branch. This went on for a good 15 or 20 minutes. Having handled pigeons caught in mist nets I can agree that they can deliver a sound, hard blow with their wings.
Thanks Bill, comments appreciated. What is holding up part II of the pterosaur article? A: a short letter, written to Science. Until I know what's happening with it, I can't risk duplicating my argument here (or anywhere).
Hi, thanks for a great post. Aside from the invaluable account of the Solitaire's appearance and behaviour by Francois Legaut (who was deprived of female company for a great stretch and and describes the Solitaire hen with an admiration approaching romantic ardour - "They have two risings on their craws, and the feathers are whiter there than the rest, which livelily represents the fine neck of a beautiful woman. They walk with so much stateliness and good grace that one cannot help admiring them and loving them") - the Solitaire makes a posthumous, fictional appearance in Patrick O'Brian's wonderful Aubrey-Maturin series, where Stephen Maturin - who also has a touching affection for Pezophaps solitarius - gives an achingly embarrassing presentation on the bird's osteology to the Paris Academy of Science.
Re the Jamaican Ibis - I think it's highly unlikely that the clubs evolved as a defence against predators (although I suppose they may occasionally have served that purpose). Jamaica is remarkably devoid of land predators: a few snakes (none venomous, and I can't see a club being all that much use against an ambush constrictor like the Jamaican boa), no seriously dangerous lizards (e.g. monitors) and no mammalian carnivores whatever (maybe a shrew or 2, I'd have to check). There are some raptors in Jamaica, but it seems pretty likely that clubs would not be very effective against an attack which would most probably come very suddenly from above and behind. So I think it's much, much more likely that the club evolved and was principally used in intraspecific competition.
PS to your PS: Darren did you ever write up your crocodile dissection for Tet Zoo? Now that I'd like to see. And Bill: maybe I'm being too hasty dismissing the predator thing, if a dove can knock a mamba about...! But then, mambas are notoriously feeble and timid are they not? They regularly get into the top ten of Animal Planet's "Nature's Deadliest Wusses - XTREME!!!!!" series. Whereas boas are rock hard and wouldn't take no from a pigeon...
Due to the small consonant inventory of Polynesian languages, Viti is the same word as Fiji.
"Should you encounter a specialised, weapon-bearing bird of any sort (either here or in the past, should you go time travelling) my advice is to be very, very careful and to try not to piss it off."
Ya. The ones toting ninja stars and RPG's, I just tell them to call my lawyer. Seriously, keep posting this stuff, as I am ignorant of tetrapod anatomy (mostly), but I soak up a lot from reading this blog regularly.
The solitaire using the wings as weapons is one thing, but it's the wearing sunglasses that makes it special (top pic).
I don't have any pictures of the attack itself, but I can certainly testify to the pugnacity of gulls. I have a scar on my left hand where a gull bit me when it stole a hot dog from me when I was four.
Fun stuff. I'm amazed that the description of Xenicibus came out only last year. I recall a talk on it by Storrs Olsen that must have been at least 15 years ago, probably closer to 20.
And on size dimorphism: I think muscovy ducks Cairina moschata might have your solitaire beat, since males can be nearly twice the weight of females. There's a fairly large size range, but at least the biggest (wild) males are nearly twice the weight of the biggest (wild) females.
"They have two risings on their craws, and the feathers are whiter there than the rest, which livelily represents the fine neck of a beautiful woman."
A real life case of Non Mammalian Mammaries??? :o
On size dimorphism in birds, i too thought of Cairina (and of various galliforms, notably Tetrao*), but wasn't certain if Galloanserae was within Neognathae...
*Is it just me, or does C. moschata have rather a lot of superficial convergences with Tetrao? Size, short legs, mostly-black plumage, red bits on face, sexual habits...
On sexual size dimorphism more generally, i've always wondered whether there is a prevailing trend across Tetrapoda as a whole. Most mammals seem to have larger males (with rorquals and hyenas as the main exceptions i can think of), most non-dinosaurian reptiles seem to have larger females, and birds seem split fairly equally, with Accipitriformes/Falconiformes and Galloanserae at opposite extremes. Are there ecological factors that predict direction of sexual size dimorphism?
Is the bird in the first picture wearing sunglasses?
I was reminded of the time I had some hatching chickens under a light and a friend was fascinated, he reached in to pick up one and got a peck from the egg tooth that drew blood- a surprising amount of blood- from beside his thumbnail. This from a bird newly hatched.
I raised chickens- chooks- for many years, and never carried a bird within pecking reach of my eyes.
What a coincidence! For the last month or so I've been wondering if any bird had ever converted to quadrupedal land movement, even in some small way (occasionally using folded wings to push off for flight, running short distances on all fours, or whatnot). And here we get a snarky look at that.
So yes, it seems pretty absurd, but what hypothetical circumstance might lead it to happen? And what would it look like? I think the type of original bird could be a factor. Something with stocky wings and weak legs that found itself flightless might be more likely to go 4-legged, like say maybe a kingfisher, as opposed to a gull (long gracile wings) or tinamou (powerful legs).
At least that radio host got it right that this was an actual dinosaur, not any of the countless extinct tetrapods often mistaken for dinosaurs.
Love the warning at the end about the badassery of birds.
There used to be monkeys on Jamaica though (Xenothrix mcgregori survived well into the Holocene). They could have been a potential danger at least to birds' eggs and nestlings.
CS Shelton: Some penguins (or at least the Magellanic penguin Spheniscus magellanicus) can actually 'run' on all fours for short distances - and quite fast, too.
Thanks for comments, everyone. In response to Kattato on the crocodile dissection (comment 5) - no, I haven't posted this yet; I mean to do so soon.
Quadrupedalism in birds: of course, no bird is properly quadrupedal, but a few species can and do use the wings as props when raising themselves off the ground, and some use them in climbing or crawling. As Dartian notes, penguins are the best example. Shoebills have been seen to use their wings as props when pulling their heads out of the water (this just after they've lunged forward to grab a fish). As is well known, the chicks of turacos and hoatzins use their clawed wings when climbing. Streaked shearwaters Calonectris leucomelas use their wings to help them climb trees: in The Life of Birds, David Attenborough says that they climb up slippery tree trunks by "pushing with their legs, scrabbling with the elbows of their closed wings" (p. 39). Any others?
I've seen an illustration of (and read about) bee eaters using their wings as props while digging, although this is not apparent from the photographs I've seen of burrowing bee eaters, probably because half the body tends to be hidden inside the burrow.
Very interesting entry! Several years ago I was the primary keeper of a Victoria Crowned Pigeon (Goura victoria) and my shins and I can testify to the wing strikes. I wasn't aware that "Violet" had such nifty physiology.
I picked up the Tet Zoo book for myself for Christmas and finished it a couple weeks ago. Really enjoyed it and looking forward to the next one!
Echoing John Harshman, I'd like to point out that in the capercaillie Tetrao urogallus, males weigh 4-6 kg and females 2-3 kg.
Years ago, I had a pet rock dove. Got him with a broken wing, and it didn't heal perfectly. That little guy liked to fight for fun, pecks, wing strikes (always hitting with the wrist), wrestling socks like a little bulldog as he cooed menacingly. It was pretty funny, because he couldn't break the skin, but it wouldn't be fun with a bigger bird.
The only thing I'm surprised about is that more pigeon species don't show structural modifications in response to this behavior. Has anyone done an anatomical series on pigeon wrists? I'll bet there are a lot of thickenings and callosities out there.
...and in the great bustard Otis tarda, the sexual size dimorphism may be even greater; males typically weigh 10-16 kg and females 3.5-5 kg.
Having been attacked by angry birds twice I can well appreciate how formidable they can be. My first was by a male ruffed grouse along a pathway in beautifully wild and remote Southeast coastal Alaska. He repeatedly,fearlessly and ferociously flew with head (its bright orange crest erect), wings and spurred feet directly into me and others as it defended its territory along a well used social trail. It did this repeatedly for a few weeks, and while the idea was hilarious on the face of it, considering we were deep in moose and brown bear territory, but quite intimidating none the less.
My second attack was from an enraged red rooster as I unsuspectingly entered a barn in rural Indiana. The flurry of rust red feathers and his throaty squawk were alarming enough to startle me but then I felt what might have been a wing, or maybe it's leg spur, but it feld like I'd been hit with a well delivered blow from a piece of iron re-bar, I don't really know, but it left a contusion on my ankle and I was seriously limping for at least a month. It seems funny to be attacked by a bird, but the bruise was no joke, and you can believe that I now give roosters a wide birth in tight situations, and vowed one day I'd make that particular guy into soup.
I think that restoration is simply based on an illustration of a crowned pigeon Goura from Christopher Perrins' The Illustrated Encyclopedia of Birds: The Definitive Reference to Birds of the World (1991) (apart from being a mirror image, the posture is near-identical).
Stevethehydra (sorry, I didn't see your comment about Tetrao until now; apparently it ended up in Darren's spam folder):
You may want to check out:
Ralls, K. 1976. Mammals in which females are larger than males. The Quarterly Review of Biology 51, 245-276.
Doug: 'Angry birds', eh? That sounds like a good idea for a video game. Oh, wait...
Almost forgot to ask...
Did you by any chance have this recent incident in mind when you wrote that?
Shouldn't this be part IV, from the links at the end you've already got a part III in this series...
Thanks for the responses to my question, everyone! I'm interested to see the penguin run, but haven't been able to find it on youtube yet. I didn't know about turacos. Good stuff!
Off to work now. *sigh*
Wouldn't any species that regularly used its wings for either locomotion or fighting tend to lose its feathers in relevant areas, either in the long term through evolution or in the short term from simple wear and tear?
Mike -- well, penguins don't lose their wing feathers, and they use their wings for locomotion on land at least part of the time. Then again, their feathers are highly adapted to their marine lifestyle, and this may make them more able to cope with the strain than other feather types.
On penguin feathers and further off topic, they examined fossil melanosomes to determine that extinct mega-penguin (I. paracasensis) was not black and white like the extant varieties.
I find that very cool. As a more seal-sized animal it may have been better served by drab coloration, I think, giving us another example of convergent evolution.
Kind of like the dark/light patterning of Sinosauropteryx prima, so reminiscent of similarly sized, totally unrelated mammals of today.
Wow, I've missed a lot!
I'll have to check out the Goura pigeons we have at the zoo. I know some of the chicks are getting feisty.