It seems they “democratically” short circuit when it’s time to leave.

On cold, dark winter mornings, you can sometimes hear small, black crows—known as jackdaws—shout loudly at each other. The birds can make a huge noise and then, almost simultaneously, take to the skies around sunrise. In a new study, researchers have set out to find out what these noisy jackdaws are talking about right before departure. And the answer may surprise you.

All at the same time

It is not easy to take off with hundreds of birds at the same time. Yet chewing regularly manages to do this. For example, it appears that the jackdaws often take off en masse, with hundreds of birds taking to the air within 4 seconds of each other.

Study

To properly study this remarkable behavior, researchers made audio and video recordings at six different chewing roosts in Cornwall, England. The population size ranged from 160 to nearly 1500 birds. So not only are the groups particularly large, they also include birds of different ages, sexes, family groups and colonies, all scattered across the treetops. The researchers then listened carefully to the calls of all these birds before and immediately after take-off.

Bandage

The research team found that there is a close relationship between the intensity of the call and the exact time of departure. Before the birds leave their sleeping place, there is a buzzing noise for at least an hour, which reaches a peak just before departure. And now the researchers finally know what the jackdaws are talking about. The cackling allows the birds to effectively synchronize their daily start.

harder and harder

How do they do that? The loud calls make the jackdaws seem to indicate their readiness to leave. The noise gets louder and louder as more birds make themselves heard and indicate that they are ready. And this then results in them all taking to the skies at the same time. It means that the jackdaws short circuit with their screams in a ‘democratic’ way when it’s time to leave. “Like humans, large animal groups use decision-making processes to overcome their individual differences and achieve a kind of ‘democratic’ consensus,” explains researcher Alex Thornton.

Test

To test this theory, the researchers played the calls of their congeners in an attempt to advance the time of departure. And that indeed seems to work. By adding extra screams to the mix, the birds flew an average of 6.5 minutes earlier than they would have otherwise.

no consensus

Incidentally, the jackdaws do not always agree on when it is time to go. On a few occasions, the noise did not build up sufficiently, indicating that the birds apparently failed to reach an agreement. As a result, the birds did not all fly at once, but in small groups.

Advantages

That in itself is not a very strange observation. It is unlikely that hundreds of different birds naturally prefer to leave at exactly the same time. And yet staying together has its advantages. For example, they reduce the risk of being caught by a predator.

All in all, the researchers’ study offers interesting new insight into how animals make decisions and come to consensus, which in the case of the jackdaws results in a beautiful mass movement. However, the researchers are not finished yet. In future studies, they hope to find out how human activities might influence observed dynamics. “Human influence on wildlife is increasing,” Thornton says. “And so we want to better understand whether and how human disturbance – for example from light and sound pollution – affects the ability of animal groups to communicate and reach agreement.”