(ORDO NEWS) — Autumn is the time when birds gather in large flocks. Sometimes the result is a beautiful phenomenon: an aerial “dance” in which the flock moves as one living being.
It is called murmuration, and scientists have been trying to solve its riddle for many decades – and even use it in engineering.
“Murmuration” in translation from Latin (murmuratio) literally means “muttering”. This name was born from the sound into which the rustle of thousands of wings merges during the flight.
Murmurations can usually be observed about an hour before sunset in autumn, winter and early spring when the birds are near the roosting area. Sometimes they last about an hour. Most often, starlings arrange murmurations.
One of the mysteries is why birds do this. After all, for a normal flight you need a lot of energy, and birds spend it extremely efficiently. But in the case of murmuration, it seems that there is no practical sense.
The birds simply disperse and gather together – like dancing couples of people or a crowd in a stadium. But, unlike the fans, these movements are not rehearsed – everything happens spontaneously.
The flock breaks up into pieces and merges again. Figures are obtained that sometimes resemble a drop, sometimes a figure eight, and sometimes even one giant bird.
At the same time – and this is another mystery – the birds fly quite quickly (up to 50 km / h), but do not collide and do not go astray. Murmurations do not have a leader, and all movements are regulated by individual individuals.
Telepathy or discipline?
In the 1930s, famed ornithologist Edmund Selous suggested that birds that form murmurations use a kind of telepathy to communicate their intentions throughout the flock.
“They have to think collectively, all at the same time … it’s like a simultaneous flash in many brains,” he wrote in his book Thought Transfer (or Something Else?) in Birds.
However, over time it became clear that this was not entirely true. In the 1950s, experts studying the collective behavior of insects, fish, and other animals found that group movement was more of a remarkably fast response to changes in the actions of others in the pack.
“There are two ways in which the behavior of a large group is controlled,” explains Mario Pesendorfer, a researcher at the Smithsonian Center for Migratory Birds (USA). “There is a top-down effect when the leader sets the movement of the entire group.
Like during a concert, when a person on stage starts to clap , and the crowd picks up. Murmurations work on the principle of “bottom-up”: individual birds influence their neighbors, and the movement is transmitted to the whole flock.”
But it is obvious that in a flock of 1,200 individuals, one bird cannot keep track of everyone. How is this degree of coordination achieved?
In 2013, Italian physicists studied more than 400 photographs from several videos, determining the position and speed of birds in a flock.
Based on this, they calculated the optimal number of neighbors that each bird keeps track of. Turns out there are seven. In turn, changes in one group are quickly transferred to others, and the entire pack begins to rebuild.
A million around and three in my mind
To find out what is happening inside the murmurations, some researchers shoot them with several cameras at the same time.
They then use computer programs to track the movements of individual starlings and create 3D models of the flock.
It turns out that the birds within the flock are not as tightly grouped as it might seem from the ground – there is room for maneuver. They are also located randomly.
For example, they fly closer to their lateral neighbors than to those in front and behind. Those birds that are located on the edge often “dive” deep into the flock.
Gradually, scientists found out that an individual, when moving, focuses on three zones:
- “Zone of attraction” – the area to the nearest bird in front
- “Repulsion zone” – an area where a collision with neighbors flying along their own “lanes” is possible
- “Angular alignment zone” – a group of seven neighboring birds that serve as a reference point for the direction of flight
The secret of how the flock achieves such smooth movements is in the high temporal resolution of the bird’s eye. The light-sensitive cells in the retina take time to fire up to respond to a light stimulus.
Because of this, our brain can only process a limited number of stimuli per unit of time. This is the resolution. In birds, it is much higher than in humans.
That is why, for example, a bird is so difficult to catch: out of the corner of its eye, it sees much more movements than we do, and reacts much faster. Interestingly, this model works not only for birds.
Other parameter values included in the model may give results similar to the movement of schools of fish or a swarm of bees. However, they may have other reasons to do so.
The best defense is in the pack
Why do murmurations happen in principle? After all, birds do not exercise like this just to please us and our subscribers in social networks. But you won’t get into their heads either and you won’t take an interview.
This is where amateur science comes to the rescue. From 2014 to 2016, scientists at the Royal Biological Society collected an unprecedented amount of data from amateur birdwatchers around the world.
Volunteers submitted reports from 23 countries covering over 3,000 murmurations. On their basis, experts have compiled a complete description of the conditions under which such behavior occurs.
Scientists came to the conclusion that, first of all, murmurations perform the function of protection against predators.
Birds gather together to search for food or rest before the flight. Huge aggregations naturally attract predators such as hawks.
Like many flocking creatures, birds rely on their numerical superiority in their defense. This is called the “dilution effect”: in a flock, the likelihood of an individual bird becoming prey is greatly reduced.
When faced with a potential predator, starlings lower their V-shaped wings and change direction abruptly, much like a school of small fish swerves sideways when confronted by a shark or other large fish.
Thus, the flock remains intact, but at the same time does not allow the predator to fix any specific target. The larger the group, the faster it reacts to the approach of a predator.
From starlings to robots
Back in 1986, Craig Reynolds, a computer scientist at the Massachusetts Institute of Technology, created a program that counts the movement of a flock of birds and fish according to the principle of murmuration.
This program served as the basis for realistic animation – for example, already in the 1992 Tim Burton film “Batman Returns”, a flock of bats was created in this way.
More curious examples relate to the coordinated work of robots and other automation. The ability of starlings to evade the enemy is highly demanded in military operations.
For example, LOCUST technology, developed for the US Navy, is a swarm of drones that can block enemy communications and deplete air defense resources by diverting their fire.
While drones do not directly mimic the behavior of starlings during murmuring, they do rely on other mechanisms of swarming behavior.
And the goal is the same – due to the accuracy and exchange of information, protect yourself from the threat.
Existing air defense systems are not capable of withstanding groups of several hundred drones. Due to this, drones can break through to the target and transmit information about it to the operator.
Another area is the interaction of unmanned vehicles on the roads. Studying the mechanics of bird swarming behavior could allow cars to move through traffic more efficiently, saving fuel and time, and avoiding accidents.
For example, engineer Santosh Devasia of the Boeing Advanced Research Center proposed a model of network behavior in which each participant uses current and past information from neighbors to infer a common goal, and fine-tunes their own behavior, just like birds.
This model, according to Devasia, could have many applications – from the work of robotic loaders in industrial warehouses to mail drones and satellites used in sensing.
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