Death by toxic goose. Amazing waterfowl facts part II


Yesterday we looked briefly at goose digestion. Pretty incredible stuff, I'm sure you'll agree. Hey: wouldn't it be weird if some waterfowl were poisonous? Yeah, wouldn't it. Well... guess what?

One of the most dangerous birds in the world - I'm not kidding here - is the African spur-winged goose Plectropterus gambensis [the adjacent painting - from wikipedia - is by Louis A. Fuertes, one of the greatest zoological artists of all time]. Weighing as much as 7 kg, this formidable bird (not a goose in the strict sense, but a member of the shelduck/sheldgoose clade Tadorninae*) bears sharp spurs on its wrists. The birds use these in attacking both other spur-winged geese, and other waterfowl (at least in captivity: a captive individual kept at Slimbridge maintained a territory on top of a small hill. Waterfowl of other species would sometimes climb the hill, get attacked, and die from their injuries). It's quite plausibly dangerous to people, but I can't find any explicit statements on that [in the stuffed specimen shown below - from Scientific-web - the wing spur is visible at the wrist joint].

* Its superficial similarity to the Australasian Magpie-goose Anseranas semipalmata meant that it was once classified alongside this species. It was also thought intermediate between screamers and anatids during the 1860s, and affinities with true geese have been suggested at times.


Anyway... as if this isn't bad enough, members of this species can sometimes be poisonous. But I don't mean that they can inject venom with their wing-spurs, or anything like that. Rather, some populations (those in the Gambia) feed on a poisonous beetle (specifically, a member of the blister beetle group (Meloidae)), and then sequester the beetle's poison into their own tissues (Bartram & Boland 2001). Blister beetles are well known for producing the toxin cantharidin, small amounts of which (as little as 10 milligrams) cause death in humans. The effect of cantharidin on the urinary tract (it results in swelling of the genitalia) means that people have been using it as an aphrodisiac for centuries; the Spanish fly Lytta vesicatori is a blister beetle. So the result of blister beetle ingestion by spur-winged geese is that their flesh is toxic. Eating one can - apparently - result in death (Wanless 2001) [Plectropterus in flight shown below].


While the poisonous tissues of several passerines - notably the various pitohuis, the Ifrita Ifrita coronata and the Rufous shrike-thrush Colluricincla megarhyncha of New Guinea - is now quite well known (this was covered on Tet Zoo back in 2008), they aren't alone and several other birds are also known to sequester toxins from various animal and/or plant prey. Quail Coturnix coturnix are known to be toxic when on migration, but only certain populations are, and only on part of their migratory journey (e.g., those flying from west Africa to Europe are toxic; those going from eastern Africa to Europe aren't toxic, but are when they return to Africa in the Autumn). Being poisoned by quail even has a name (coturnism): there are accounts of it in the Bible, and it was so common in the Roman Empire that the eating of quails was banned in the 1st century (Bartram & Boland 2001).

More waterfowl facts in the next article. For previous Tet Zoo entries on waterfowl see...

Ref - -

Bartram, S., & Boland, W. (2001). Chemistry and ecology of toxic birds. ChemBioChem, 2, 809-811

Wanless, R. 2001. Red-billed woodhoopoes go on the defensive: preening power. Africa - Birds & Birding 6 (1), 55-59.

Taxonomic note: it isn't quite clear to me that Plectropterus is tadornine, unless you expand the term to include the sea ducks.

By John Harshman (not verified) on 19 Jun 2010 #permalink

While the cellulolytic capabilities of the galloanseriformes seems limited, i suspect they are in general poorly understood. There are some early studies suggesting that several waterfowl and fowl have abilities to break down cellulose through bacterial symbionts in the cecae. However, this may be more to facilitate release of nutrients by breaking cellwalls than to extensively use cellulose break down products. Certainly some dinosaurs seem to use microbial flora in digestion.It was demonstrated that the gut bacteria of Honeyguides help in wax digestion. But some workers like Diamond claim that they are parasites and the birds have endogenous wax digesting enzymes. If this were true then it would me the origin of some unusual biochemistry whose origins certainly need exploration.

I am always surprised, though I shouldn't be, by the great erudition of the average TetZoo reader. Sorry to drag things down with my fine arts degree.

The spurs are fascinating! How does such a small weapon kill an opponent? Does its structure (barbs etc.) cause a gory wound? Are they homologous (am I using that right?) to the claws birds used to have, or novel structures? If novel, what are they made from? Are there better pictures to be found anywhere? Why do these birds and certain ratites never get mentioned when people are talking about hoatzin fingers?

Zoology is just too interesting.

By CS Shelton (not verified) on 19 Jun 2010 #permalink

Plectropterus not a tadornine? I will admit that I was heavily Livezeyised during my formative years; when I think of the affinities of Plectropterus, I associate it with Sarkidiornis in a tadornine Plectropterini clade (as per Livezey 1996, 1997). I even dug out Callaghan & Harshman (2005), where Plectropterini is again within Tadorninae. However, I can think of some phylogenies where Plectropterus is outside tadornines + anatines - what do you mean by the sea duck comment?

Refs - -

Callaghan, D. & Harshman, J. 2005. Taxonomy and systematics. In Kear, J. & Hulme, M. (eds) Bird Families of the World: Ducks, Geese and Swans. Vol. II. Oxford University Press, pp. 14-26.

Livezey, B. C. 1996. A phylogenetic reassessment of the tadornine-anatine divergence (Aves: Anseriformes: Anatidae). Annals of Carnegie Museum 65, 27-88.

- . 1997. A phylogenetic classification of waterfowl (Aves: Anseriformes), including selected fossil species. Annals of Carnegie Museum 66, 457-496.

CS Shelton: keep an eye on the site, all will be revealed :) (in other words, an article dedicated to manual spurs, claws, clubs and knobs is coming soon).

Callaghan & Harshman was conservative, just what could be gleaned from published sources. I'm afraid the analysis I'm using is still unpublished, for which I'm truly sorry. But it turns out that Sarkidiornis and Plectropterus are not closely related; the former is anatine in the broad sense, the latter tadornine in the broad sense. And the broad sense includes pochards in the first case and sea ducks in the second. While the data don't conclusively say Plectropterus isn't tadornine in the narrow sense, they don't support it either.

By John Harshman (not verified) on 19 Jun 2010 #permalink

Some Australian birds should not be eaten: bronzewing pigeons can sequester the poison 10-80 from native plants. Eat any of that, and you're a gonna. Unless you're a native marsupial, some of which are immune to 10-80, which means it makes a great poison when baiting for foxes - no native mammals killed.

@Darren- I can't wait!
@Bill- That's really cool. I guess Australia's absurdly poisonous wildlife is good for something...

There's a Cure lyric about "poison birds" which was probably just so much poetry and didn't mean anything. I told my girlfriend there's poison birds (the New Guinea species) but they hadn't been discovered when Robert Smith wrote that line, but now I find out dietarily poisonous birds were known from antiquity. Ha! That'll teach me to talk like I know something. Obviously, Mr. Smith was talking about quails...

By CS Shelton (not verified) on 19 Jun 2010 #permalink

Spurs on wings: Australian Masked Lapwings were known as Spur-winged Plovers when I was young. I heard some kids being scolded for getting home late - "Why didn't you cut across the golf-course?" "We tried, mum, but we got ploved."
They fly at you screaming and biff you round the head. Painfully.
Bronzewing Pigeons are only poisonous in Western Australia. Only the bones are poisonous - the meat is all right, but the bones have accounted for many scrap-eating dogs.

That spur-winged geese beat the shit out of other waterbirds with their wings reminds me a lot of the steamer ducks that Darren blogged about previously here.

I was immediately struck by the resemblance to Anseranas when the post came up with the top painting, and thought it mighty curious because Anseranatidae is (extantly) monotypic. I'm no expert on waterfowl (Trevor Worthy's my go-to guy) but black-and-white plumage, with red or yellow beak and exposed facial skin, are present in near-basal members of most of the major lineages of anseriforms (including screamers, magpie goose, swans, the subject of this post), so those are probably ancestral conditions. (Peter Trusler used a pied colour scheme for reconstructions of Dromornis on the cover of Murray & Vickers-Rich's Mihirung book, which I applaud)

Does the close family resemblance of Plectropterus and Anseranas reflect relative lack of change in both lineages since the Paleocene or so, or is there a good reason to infer convergence due to independently derived habits?

The Rodrigues Solitaire (now sadly extinct) had something similar, a knobby outgrowth on the wrist part of the wing, with which males apparently bashed each other. This one was a Columbiform (related to pigeons and doves). Plovers are Charadriiforms, so this sort of thing apparently evolves independently in different groups ...

By Willem van der Merwe (not verified) on 20 Jun 2010 #permalink

George: Probably a rhizomyine, or bamboo rat. _Rhizomys sinensis_ is perhaps most likely, but I'm not quite sure how to tell them apart (there are four species in total, three of which occur in China).

By Jelle Zijlstra (not verified) on 20 Jun 2010 #permalink

Considering that Anseranas and Plectropterus are widely separated on the phylogenetic tree, it would be highly unparsimonious to suppose they shared any primitive characteristic that had been lost many times independently by all the lineages in between. What would cause them to converge is unclear, but there are 150 or so species of ducks, and maybe it's just us imposing a pattern on contingent variation. Would you count Muscovy ducks (Asarcornis scutulatus) as a third example?

By John Harshman (not verified) on 20 Jun 2010 #permalink

Spurs on wings appeared also in other spur-winged lapwings, jacanas and perhaps some forms I forgot now.

There is also a subfossil thing called Club-winged Ibis, but I only know the rather intriguing name.

I'm all over those club-winged, spur-winged and knob-winged plovers, pigeons, ibises, waterfowl etc. - you guys should stop spoiling the surprises for everyone else :) More soon, with neat pictures.