LONDON Magpies can recognise themselves in a mirror, highlighting the mental skills of some birds and confounding the notion that self-awareness is the exclusive preserve of humans and a few higher mammals.
It had been thought only chimpanzees, dolphins and elephants shared the human ability to recognise their own bodies in a mirror.
But German scientists reported on Tuesday that magpies -- a species with a brain structure very different from mammals -- could also identify themselves.
"It shows that the line leading to humans is not as special as many thought," lead researcher Helmut Prior of the Institute of Psychology at Goethe University in Frankfurt told Reuters.
"After finding this kind of intelligence in apes, many people thought it had developed once in one evolutionary line with humans at the end. The bird studies show it has developed at least twice."
The discovery of self-awareness in magpies follows a 2002 study in which a crow stunned researchers with its tool-making skills, by twisting a wire into a hook to lift food from a tube.
Prior and his colleagues tested their magpies by marking the birds' bodies with a red or yellow dot that could only be seen in a mirror. They found the birds regularly scratched the mark on their body, proving they recognised the image in the mirror as themselves and not another animal.
To ensure they were actually seeing and reacting to the mark, and not just investigating what had been done to them, a "sham" black mark was used as a control that was invisible on the birds' dark feathers.
The result throws into question some basic ideas about how our brains work.
In particular, it had been thought that the neocortex brain area found in mammals was crucial to self-recognition. Yet birds, which last shared a common ancestor with mammals 300 million years ago, do not have a neocortex, suggesting that higher cognitive skills can develop in other ways.
Prior believes parrots, too, may yet show hidden mental skills -- but it is the crow family, which includes magpies and jays, that is the smartest.
"Crows have really huge brains compared to other birds," he said in a telephone interview.
The research was published in the Public Library of Science journal PLoS Biology and is available online here
(Editing by Mary Gabriel)