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Magpies point to danger

Clever birds Pointing may be rude in the human world, but a new study has found magpies use it to communicate danger.

In doing so, they may be the first example of a species other than humans and chimpanzees to use this communication method, proving that they have higher cognitive abilities than previously thought, says Professor Gisela Kaplan from the University of New England.

Pointing is thought to be related to the development of language but "up until now all the literature has assumed that you need hands and arms to gesture," says Kaplan.

"But I don't think that's true anymore and [this study] it undercuts that assumption," she says of her research, which appears online ahead of publication of the upcoming issue of Current Zoology.

It was a chance discovery that magpies (Gymnorhina tibicen) appeared to call out and point towards a wounded wedgetail eagle under a tree that led Kaplan to conduct further research into the birds' behaviour.

To test her theory that the behaviour was more than just mere imitation, she set up three scenarios on three different groups of birds and repeated them the following year.

On the lookout

In the first scenario Kaplan placed a realistic-looking stuffed eagle in an open field to simulate a naturalistic setting. In the second scenario she placed the eagle under shrubs or trees so that the eagle was visible, but couldn't be swooped, and in the third scenario she completely hid the eagle in shrubbery.

In each case she observed the birds' behaviour noting whether they held their body in a pointing position for a prolonged period, exhibited exaggerated side-to-side head movements, looked up in the sky, or turned their heads and held their eye gaze in the direction of the eagle.

Kaplan says the magpies exhibited more pointing behaviour when the eagle was completely hidden from sight.

"The more naturalistic it got the more the normal responses [such as swooping] took over. But during the hidden condition, even though it was an unusual event ... they can communicate at an even more intense visual level."

According to Kaplan, when the first magpie spotted the eagle it sent out an eagle-alert call and pointed towards the eagle. The next magpie to fly in would either look at the first bird or look up in the air to where it would expect to find the eagle. It would then turn back at the first magpie and follow its body direction line of gaze until it too spotted the eagle and started pointing. The first bird would continue to point until the last bird, which didn't point joined the group.

"They actually used the direction of the other to then find the eagle. They looked up, they looked in the direction of the magpie and when they finally spotted it then they adopted that posture," says Kaplan. "It was really quite unmistakeable."

Not swooping or imitating

She says the pointing behaviour cannot be explained as a swooping posture or an act of imitation.

"The pointing is one line of the neck and beak with the back downwards which is very difficult to maintain because they vocalise at the same time and give an eagle alarm call," says Kaplan.

"They didn't just imitate each other by lining up on a branch on a perch, they were somehow always parallel to the other one.

"By ruling out all the other [explanations] there is only … one simple explanation possible that the discoverer of the eagle in that unusual hidden position was trying to communicate to the others.

"So it's very clear that there's a cognitive process happening."

Dr K-Lynn Smith who is a behavioural biologist in the School of Biology at Macquarie University says the research is very interesting and could generate more studies in the area.

"It is entirely probable that birds use referential visual signals to indicate events that are external to themselves," says Smith.

"We know from work with chickens that they use visual display to use proximal pointing with their beak to say 'this food item is at my feet so come and get it'."

"So I think it's entirely possible that birds may be able to follow body posture and gaze direction," she says.