Jackdaw mobs flip from chaos to order as they grow

Date: November 15, 2019

Source: University of Exeter

Chaotic mobs of jackdaws suddenly get organised once enough birds join in, new research shows.

The birds form mobs to drive away predators near their nests, and are initially disordered.

But the new study, by biologists at the University of Exeter, physicists at Stanford University and computer scientists from Simon Fraser University in Canada, shows a dramatic switch to "ordered motion" once the group reaches a certain density.

The study also reveals that jackdaws follow different rules when mobbing predators than when flying to winter roosts.

"Traditionally, it is thought that flocking -- and other collective behaviour like swarms, fish schools and human crowds -- occurs when each individual follows an identical set of rules to every other in the group," said Dr Alex Thornton, of the Centre for Ecology and Conservation on Exeter's Penryn Campus in Cornwall.

"This study shows that these rules are actually flexible.

"When flying to their winter roosts, jackdaws follow what we call 'topological rules' -- meaning that they respond to the movements of a fixed number of neighbours, and groups remain ordered regardless of how many birds are flying together.

"When mobbing a predator, however, the jackdaws instead use 'metric rules' where they respond to all the neighbours that are within a given distance. Here, we see order emerging from chaos.

"Jackdaws issue an alarm call to draw other birds to the mob, and at first these groups are completely disordered.

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Angry birds: Size of jackdaw mobs depends on who calls warning

Date:  May 10, 2018

Source:  University of Exeter

Jackdaws recognise each other's voices and respond in greater numbers to warnings from familiar birds than strangers, new research shows.

The birds produce a harsh "scolding call" when they spot a predator, calling fellow jackdaws to mob the intruder and drive it away.

University of Exeter researchers have discovered that each bird has a unique call, and the size of the mob depends on which bird calls the warning.

The scientists played recordings of individual calls and found that the largest mobs assembled when birds heard the cry of a member of their own colony.

"Joining a mobbing event can be dangerous, as it involves approaching a predator, so it makes sense for individuals to be selective in whom they join. Our results show that jackdaws use the ability to discriminate between each other's voices when deciding whether to join in potentially risky collective activities," said Dr Alex Thornton, of the Centre for Ecology and Conservation on the University of Exeter's Penryn Campus in Cornwall.

"We also found a positive feedback loop -- if birds joining a mob made alarm calls of their own, this in turn caused more birds to join in, magnifying the size of the mob."

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Nurse snaps “first known picture” of white jackdaw in Scotland

By Annie Butterworth -

September 13, 2017

A NURSE out for a stroll has captured what may be the first known picture of a white jackdaw north of the border.

The bird, part of the crow family, is normally black or dark grey but Sheona Murray’s stunning snap shows a gleaming white jackdaw.

Only 10 white jackdaws have been spotted in the UK since the year 2000, according to experts.

Photo: Sheona Murray

The bird, part of the crow family, is normally black or dark grey but Sheona Murray’s stunning snap shows a gleaming white jackdaw.

Sheona’s remarkable bird is thought to be the first actually photographed in Scotland and is almost certainly the northernmost sighting.

The jackdaw, gleaming white apart from a smudge of grey on its tail, was snapped earlier this week in Sheona’s home village of Rogart, Sutherland, about 70 miles south of John O’Groats.

Sheona, who is also a keen wildlife photographer, caught an inquisitive, black cow in the background, further enhancing the remarkable appearance of the jackdaw.

Birds of its kind tend to be especially rare because they are often attacked and killed by “normal” members of their own species.

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