'Democratic' jackdaws use noise to make decisions

Image source, Getty Images

Jackdaws use a process to decide when to leave their roosts.

Thousands of jackdaws can fly in the morning skies in winter, creating a black cloud of creatures.

The birds call out when they want to leave.

The birds fly away when the noise reaches a critical level.

Alex Thornton, a professor of cognitive evolution at the University of Exeter, said that it was a rare insight into how animals make group decisions.

Prof Thornton explains that when a bird calls, it can either cast a vote or signal it wants to leave. The decision to leave rests on two things.

The first is noise volume and the second is how fast the noise levels increase.

The roost of thousands of birds form one of the UK's most famous winter events when they reach consensus.

The researchers say that the roost leaves earlier when the noise levels rise.

In Norfolk roosts of 40,000 jackdaws have been observed.

Prof Thornton suggests that Jackdaws want to leave the trees together because they are useful for information-sharing.

You can tell if another person is well-fed or if they have eaten by listening to their calls. Prof Thornton says that you might know that a bird is worth following to find a good place for a meal.

Image source, Alex Thornton

Scientists attached audio recorders to the trees where jackdaws roost in Cornwall.

The researchers analysed the sounds and compared them to times when the birds left the trees.

The scientists played back the recordings at jackdaws and found that the roosts responded to the sounds six minutes earlier on average.

When wind noises were played, the birds did not leave, indicating that jackdaws responded to calls.

Prof Thornton explains that scientists haven't studied it in detail.

He says the findings will help scientists understand the effect of human activities on animal populations.

Light and noise pollution may be interfering with animals ability to communicate with each other, as people are creating disturbances to birds through light and noise.

Imagine a roost near a busy road. Prof Thornton explains that if the birds can't hear each other and can't form a consensus to leave together, it could have a big impact on their population.

The journal Current Biology published the research.