Several powerful neurotoxins, including some new to science, have been discovered in the skin and feathers of six New Guinean bird species.
The toxins are very similar to those in the skin of some Amazonian frogs, say the researchers who found them. They deter predators, but the birds may also use them to protect their eggs.
The team found the highest level of toxins in the belly, breast and leg feathers, which are most likely to brush against eggs in the nest.
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鈥淭he toxins also accumulate in the down, which the birds presumably use to line their nests,鈥� says Thomas Spande of the National Institutes of Health in Bethesda, Maryland.
鈥淓ggs in the nest would come into contact with the down. And if a snake was trying to eat an egg whole, it would come into contact with the toxin and probably spit it out again.鈥�
Colin Bibby of BirdLife International says: 鈥淲e knew that marine animals commonly produce defensive toxins, and it does occur in frogs. But this discovery shows really how shockingly little we know about life on this planet.鈥�
Chilli peppers
Jack Dumbacher of the Smithsonian Institution in Washington DC led the new research. He identified the first known poisonous bird 鈥� a species of the songbird, Pitohui 鈥� in 1992. Now his team has found similar toxins in the skin and feathers of four more species of Pitohui, as well as the sole species of another genus, the Ifrita.
Pitohuis are about the size of a blackbird, whereas the Ifrita is around the size of a sparrow and both are common in New Guinea. Very little is known about their lifestyles, diets, or predators.
New Guineans occasionally eat the birds. 鈥淭hey say it tastes like eating very hot chilli peppers,鈥� Spande told New 杏吧原创. 鈥淭hey usually only eat them when they鈥檙e desperate 鈥� and they remove all the feathers and as much of the skin as possible.鈥�
Potent poison
In an earlier study, Dumbacher injected a mouse with 10 milligrams of skin from the first Pitohui species he studied. The mouse died after 20 minutes.
But the chemicals are only deadly if they are introduced directly into the bloodstream 鈥� frog toxins are used to tip a poison darts, for example. They are mostly broken down during digestion, says Spande. 鈥淭o a predator, such as a snake or rodent, the bird probably just tastes bad.鈥�
The team does not know how the toxins are produced. 鈥淭he chemicals could be obtained in the diet, or they could be down to some symbiotic microorganism,鈥� Spande says.
The Ifrita is thought to eat only insects, but the Pitohui also eats berries. Dumbacher recently returned to the US from New Guinea with samples of all the insects and berries the birds could conceivably eat. 鈥淲e have a mountain of stuff,鈥� says Spande. 鈥淣ow we have to analyse it.鈥�
More at: Proceedings of the National Academy of Sciences, online edition, 17 October
