Monday, 27 January 2014

Obscure bird of the week: Hooded Pitohui

Great discoveries have the amusing and thoughtful tendency to happen completely by accident. Take George De Menstral, a Swiss engineer who, whilst removing plant burrs from his dog in 1942, was hit by the proverbial brainwave. Under the microscope, the burrs revealed tiny hooks which attached to tiny loops, such as dog fur, and thus Velcro was born. Then, of course, there is penicillin, the miracle antibiotic which was discovered by Mr A Fleming's lacklustre approach to cleaning his lab before he went on holiday.
Who knows what would have happened if he'd been tidier?

So take the case of Mr Jack Dumbacher, an American research biologist who, in 1989, was studying that avian drag-queen, the Raggiana Bird-of-paradise Paradisaea raggiana in New Guinea. 
Standard procedure for ornithological research is mist-netting to catch the birds, and this comes with the added interest/hindrance of 'bycatch' species. Some of these collateral birds were Hooded Pitohuis Pitohui dichrous (say pit-eww-ease), attractive, thrush-sized songbirds, with an orange-black colour scheme like that of the American Icterid Orioles (quite conversely, pitohuis are sometimes placed in the family of Oriolidae: the old-world orioles).


As any bird ringer will tell you, even small passerines have the ability to draw blood in the hand. This was no exception with the captured pitohuis, which left stinging cuts on Dumbacher and his colleagues, which they automatically sucked to clean the wounds.
This proved to be an interesting move, as they all experienced a numbing, tingling sensation in their mouth, which they recognised as coming from a toxin.
Making sure that the toxin was not from some other source, such as a plant, daring Dumbacher licked a pitohui feather and found the same sensation to last for hours on his tongue. Could this be the first scientifically confirmed* poisonous bird?

In 1992, feathers that had been sent to chemists were identified to contain batrachotoxins, the same neurotoxin found in the world's funkiest amphibians, the poison dart frogs over 10,000 miles away in South America. The pitohui's plumage was tested and the poison on each of its feathers was found to be enough to kill several lab mice, confirming the bird's new landmark status. It even made front cover of that year's Science magazine.

1992 Science cover - pitohui power!

How the bird became toxic was not confirmed until 2004, when the now pitohui-possessed Dumbacher found, thanks to observant New Guinea villagers, that the birds were feeding on equally orange-and-black melyrid beetles, which contain, yep, batrachotoxins.

The batrachotoxin in question, one for all you chemists.

This confused ornithologists somewhat: the birds have gone to a lot of effort into becoming poisonous, having to first build up resistance to the melyrid beetle poison, and then the reason why they developed this rare defence strategy is not really clear. They're birds; escaping predators requires simple flight, surely. Even if they were caught by a predator, the toxin is not enough to kill the attacker, simply giving them a foul taste in their mouth. Is the poison really to deter predators? Could it be an extreme form of pest control, preventing parasites establishing on the bird's skin and feathers?
It's clear that the world of the Hooded Pitohui (or indeed, the two other pitohui species which have since been found with strong posion) requires extensive study, but boy does it make for one manically obscure bird!

-Jonnie Fisk
Jonnie is an 18 year-old Yorkshire-based birder, invertebrate enthusiast and frustrated artist. When not being oblivious to every local rarity, he enjoys autumn vis-mig and being distracted by bugs.

*It would not be the first recorded toxic bird. Biblical accounts tell of Israelites becoming ill after consuming Common Quail Coturnix coturnix, and research has turned up some incredible facts linked to quail migration, namely that those which take the "western flyway"; Algeria to France, seem to become poisonous during the spring migration only whilst those taking the "eastern flyway"; down the Nile Valley, have only been reported to become poisonous during the autumn migration (the "central flyway" through Italy, has no associated poisonings). However, no scientific research has identified the toxin, or the source, though the plants hemlock, hellebore and Annual Woundwort have been suggested.
The 19th century naturalist John James Audubon noted that the now extinct Carolina Parakeet Conuropsis carolinensis was poisonous, stating that cats died from eating them. Though we cannot prove it, it's thought that they got some form of toxin from the seeds of cockleburs (Xanthium)

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