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.

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.

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.

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.

When the noise levels rise more rapidly, the roost