Wednesday, 12 Nov, 2008 Environment

Some Birds Can Understand the Language of Other Bird Species


Scientists from Australia claim they were able to determine how some species of birds managed to develop the ability to recognize each other's language. Together with his colleagues from the School of Botany and Zoology at the Australian National University in Canberra, associate Professor Robert Magrath discovered that fairy-wrens can learn the alarm calls produced by other species of birds, which makes it easier for them to escape predators.

The research and its results were published in the latest issue of "Proceedings of The Royal Society B." although scientists knew that some birds understand the alarm calls of other species and use their ability in order to escape danger, it was previously unknown how they developed this ability. There are several hypothesizes that aim to explain this fact.

Some researchers suggest that individual species are able to understand the alarm calls of other species due to the fact that they were born with the ability to react to calls that are somewhat similar in terms of acoustic structure. There is another hypothesis that says all birds can learn alarm calls from different species over a certain period of time.

In order to identify which hypothesis was closer to the truth, scientists played the sounds of alert calls of white-browed scrubwren to another species of birds called fairy-wrens that live side-by-side in Canberra. Alert calls of the two species are somewhat similar by they are not the same. The second step was playing recordings of white-browed scrubwren alert calls to fairy-wrens that live in 600km away from Canberra, in Macquarie Marshes, the region where scrubwren doesn't live.

"If [the response] is due to similarity, and you go to an area where fairy-wrens occur, but scrubwrens don't...and play back the scrubwren calls, they should still flee for cover," outlined Magrath.

The experiment showed that fairy-wrens living in Canberra fled but Macquarie Marshes fairy-wrens did not, which, according to Magrath, has to do with learning.

Another experiment involved playing recordings of a different alert call emitted by New Holland honeyeater. Researchers said that after hearing the calls the fairy-wrens fled, which means that they can learn calls completely different to their own. The team decided to play the alert calls of the honeyeater backwards in order to see whether the fairy-wrens could react to general acoustic aspects, such as fast repetition or peak frequency. Nearly all fairy-wrens ignored such call.

"The fact that they don't respond shows that they have learned honeyeater's call and are not responding to some general acoustic property like rapid repetition. They have a very acute perception about other species calls," said Magrath.

According to another scientist from the Centre for Neuroscience and Animal Behaviour at the University of New England in Armidale, the current research proved to be well constructed, but at the same time Professor Gisela Kaplan considers that learning is not the entire reason why birds fled after hearing the alert calls. The researcher considers that birds' brain features an "emergency pack" which includes pre-programmed reactions at birth. The pack may be constructed of neurons that produce a basic reflex when it is triggered by auditory responses.

"It could be that a certain sound, like a 6 kilohertz high-pitched frequency, is part of that basic reflex. Where the learned part comes in is to then correctly distinguish whether somebody else is simply making a high-pitch call or if it is an alarm call," said Kaplan. She added that her team played the same recordings to magpies at various distances and discovered that their reaction was different. "It depends on whether the bird's sound is coming from within the magpie's territory. The difference can be as small as two metres," she said.

Magrath considers that the ability to understand the alarm calls of other species of birds have implications for captive breeding programs.

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