Experiments by researchers at Victoria University of Technology in Melbourne, Australia, show that the oil sticks better to the iron than the birds' plumage. If the powder is sprinkled on the feathers and then combed out with a magnet, the oil comes away with the metal.

"We were quite amazed by the efficiency of the cleansing process," John Orbell, the lead researcher told New Scientist magazine.

The new technique is said to remove the oil without damaging the waterproof properties of the birds' feathers. This can be a problem with the traditional cleaning technique which involves bathing the birds in soapy water.

Orbell and his colleagues tested the powder on duck feathers coated with different grades of oil. Just one round of powder coating and magnetic combing removed 88% of light crude oils and more than 60% of the stickier, thicker grades. However, when the procedure was repeated 10 times, 97% of all kinds of oil was removed.

Portable field unit

The feathers were then examined under a microscope. Their tiny barbules were neatly aligned, as they should be, and drops of water rolled off the feathers, indicating that they remained water-repellent.

The barbules of feathers cleaned with detergents were entangled, impairing their ability to shrug off water. Magnetic cleaning was also said to be much quicker than detergent treatment, and less stressful to birds since it involved less handling.

The Melbourne team, who report their work in the Marine Pollution Bulletin, are now developing a portable field unit so rescuers can remove the bulk of the contamination at the location of an oil spill.

"Iron powder is cheap and plentiful, and both non-toxic and a non-irritant," Orbell said.