This is one of my favourite biological stories which I wrote. It was published in The Guardian. It gives budding biologists an insight into wildlife biology and freelance journalism.
Chilli-hot Songbirds
Those of you who enjoy eating foods laden with chilli may find birds from the forests of New Guinea just too hot to handle. According to locals these birds taste hotter than chilli peppers. Even breathing fragments from their feathers causes watery eyes, burning, coughing and sneezing and the smell alone can make one nauseous.
Jack Dumbacher and colleagues of the Smithsonian Institution, have discovered that skin and feathers of five species of brightly coloured pitohui songbirds including, the sour smelling black and orange hooded pitohui and the blue-capped ifrita, contain toxins known as batrachotoxins. These poisons are concentrated in feathers and skin in the belly, breast and leg with lower amounts in the less fleshy head, back, tail and wing feathers of the songbirds. Until now, batrachotoxins were only known to occur in frogs such as deadly poison-dart frogs, a poison Columbian locals use for blowgun darts.
So, why would a bird go to so much trouble to be chilli-hot? Many of the four hundred or so birds unique to New Guinea have developed a strikingly colourful plumage to attract females. Bright displays and extravagant plumes have their drawbacks since the birds’ splendour lures not only females but also hungry predators such as human hunters, snakes and rodents. By being chilli-hot these colourful songs birds can deter would-be-predators.
The bright colours of these songbirds also attract predators such as hawks, which fly overhead and snatch the songbirds from tree branches. Once tasted, though, the hawks soon associate these bright colours with an unpleasant chilli-hotness and avoid the songbirds in future.
Other pitohuis and even the young of another bird species, Greater melampittas, take advantage of this warning colouration. They mimic poisonous pitohui by sharing their bright colours. Thus although these mimics lack the chilli-hot toxins predators are fooled and won’t risk burning their mouths by eating them.
Predators such as green tree pythons and brown tree snakes hunt prey by smell and taste by flicking their tongue towards the prey prior to capture. The repugnant smell and taste of chilli-hot pitohui and ifrita birds acts as an effective snake deterrent.
Since the chilli-hot birds nest beneath the forest canopy only a few metres from the ground their eggs and nestlings are also vulnerable to predators. Ingeniously, breast and belly feathers contain the highest levels of toxins and these rub off onto incubated eggs and nestlings thereby protecting them.
Parasites can also be a problem for birds. They frequently attack birds and can damage their plumage reducing their sexual attractiveness and, hence, their mating success. Luckily, in addition to repelling predators, the toxins in the skin and feathers of the chilli-hot birds ward off feather lice and other parasites.
New Guinean songbirds aren’t the only animals to use repellent chemicals to deter predators. One well-known example of another repellent creature is the skunk. When threatened by a potential predator some skunks simply stamp their front feet, raise their tails and walk stiff-legged. Others literally throw their back legs in the air and walk in a handstand pose. The skunk then sprays the predator with a fine mist of a foul smelling liquid, which can cause sore skin, and temporary blindness in the would-be-attacker.
Even in Britain we have nasty animal surprises lurking nearby. For instance, the gentle-looking ladybird hiding amongst your garden flowers is not as harmless as it first appears. Ladybirds have toxic and very bitter yellow-orange coloured blood, which can exude from their leg joints when picked up.
Another visitor to our leafy gardens is the caterpillar of the brown-tail moth, which has a dense coat of hollow hairs. If handled, these hairs brush against the skin and cause a blistering rash. Worse still, after adults have emerged from their cocoons the irritant hairs may be blown into the air where they can cause severe eye irritations.
Most people enjoy eating birds, especially at Christmas time, and thankfully, apart from the chilli-hot birds, few other bird species are known to be toxic. Poisonous birds worth avoiding though include, spur-winged geese, some ducks and Eurasian quails. Toxins from the latter can cause nausea, muscle pain and occasional death, yet despite this, they are still favoured as a delicacy in parts of Europe. Something to ponder next time you savour a roast!
