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'Democratic' jackdaws use noise to make decisions | 'Democratic' jackdaws use noise to make decisions |
(about 11 hours later) | |
Jackdaws use a "democratic" process to decide when to leave their roosts en masse, scientists have discovered. | Jackdaws use a "democratic" process to decide when to leave their roosts en masse, scientists have discovered. |
Thousands of jackdaws can suddenly take to the morning skies in winter, creating a whirling black cloud of creatures. | Thousands of jackdaws can suddenly take to the morning skies in winter, creating a whirling black cloud of creatures. |
Researchers have now found that the birds call out when they want to leave. | Researchers have now found that the birds call out when they want to leave. |
Then when the noise reaches a critical level, it signals the roost is ready to depart, and the birds fly away. | Then when the noise reaches a critical level, it signals the roost is ready to depart, and the birds fly away. |
It's a rare insight into how animals make group decisions, Alex Thornton, professor of cognitive evolution at University of Exeter, told BBC News. | It's a rare insight into how animals make group decisions, Alex Thornton, professor of cognitive evolution at University of Exeter, told BBC News. |
"When a bird calls, it's casting a vote or signalling it wants to leave," Prof Thornton explains. The collective decision to depart then rests on two things. | "When a bird calls, it's casting a vote or signalling it wants to leave," Prof Thornton explains. The collective decision to depart then rests on two things. |
The first is noise volume and the second is the crescendo or how rapidly the noise levels increase. | The first is noise volume and the second is the crescendo or how rapidly the noise levels increase. |
Once the birds reach consensus, the roost of thousands launches from the tree within five seconds on average, forming one of the famous winter UK spectacles. | Once the birds reach consensus, the roost of thousands launches from the tree within five seconds on average, forming one of the famous winter UK spectacles. |
When the noise levels rise more rapidly, the roost leaves earlier, the researchers say. | When the noise levels rise more rapidly, the roost leaves earlier, the researchers say. |
In Norfolk roosts of 40,000 jackdaws have been observed leaving trees en masse. | In Norfolk roosts of 40,000 jackdaws have been observed leaving trees en masse. |
Jackdaws want to leave the trees together because it protects them against predators or is useful for "information-sharing", Prof Thornton suggests. | Jackdaws want to leave the trees together because it protects them against predators or is useful for "information-sharing", Prof Thornton suggests. |
"If you're flying off altogether, you might notice that another individual is particularly well-fed or you can tell from their calls that they've eaten. You might realise that's a bird worth following to find a good place for a meal," Prof Thornton explains. | "If you're flying off altogether, you might notice that another individual is particularly well-fed or you can tell from their calls that they've eaten. You might realise that's a bird worth following to find a good place for a meal," Prof Thornton explains. |
Scientists observed jackdaws behaviour in Cornwall | Scientists observed jackdaws behaviour in Cornwall |
To observe the birds' behaviour, scientists attached audio recorders to trees where jackdaws roost in Cornwall over two winters. | To observe the birds' behaviour, scientists attached audio recorders to trees where jackdaws roost in Cornwall over two winters. |
Led by Masters student Alex Dibnah, the researchers analysed the sounds and compared the noise to times at which the birds left the trees. | |
Scientists study secrets of starling murmurations | Scientists study secrets of starling murmurations |
Bird eggs suggest spring is three weeks earlier | Bird eggs suggest spring is three weeks earlier |
Britain's loudest bird makes booming recovery | Britain's loudest bird makes booming recovery |
To test their findings, the scientists played back the recordings at jackdaws and observed that the roosts responded to the sounds, departing six minutes earlier on average. | To test their findings, the scientists played back the recordings at jackdaws and observed that the roosts responded to the sounds, departing six minutes earlier on average. |
When wind noises were played instead, the birds did not leave, indicating that jackdaws responded specifically to calls rather than simply noise disturbance. | When wind noises were played instead, the birds did not leave, indicating that jackdaws responded specifically to calls rather than simply noise disturbance. |
Other birds may behave similarly but scientists haven't yet studied it in detail, Prof Thornton explains. | Other birds may behave similarly but scientists haven't yet studied it in detail, Prof Thornton explains. |
The findings will help scientists understand the effect of human activities on animal populations, he says. | The findings will help scientists understand the effect of human activities on animal populations, he says. |
People are increasingly creating disturbances to birds through light and noise pollution, which may be interfering with animals ability to communicate with each other. | People are increasingly creating disturbances to birds through light and noise pollution, which may be interfering with animals ability to communicate with each other. |
"Imagine a big roost near a town or busy road. If the birds can't hear other other and can't form a consensus to leave together, it could have big impacts on their population," Prof Thornton explains. | "Imagine a big roost near a town or busy road. If the birds can't hear other other and can't form a consensus to leave together, it could have big impacts on their population," Prof Thornton explains. |
The research is published in the journal Current Biology. | The research is published in the journal Current Biology. |
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