It is a breath taking spectacle, an awe-inspiring feat: thousands of red-billed quelea, the world’s most abundant bird species, moving in a unified dance across the sky. A sudden change of direction and a flash of silver sweeps by, another change and the cohesive mass of brown feathers morph in size and shape: thousands of tiny individuals moving in liquid magnetism. Known collectively as a murmuration, it is a phenomenon that still has many unanswered questions.
Studies have been undertaken on European Starlings that also congregate up to thousands in the British Isles. With new developments in computer generated simulations and graphics, scientists have been able to theorise through 3D positioning and velocities exactly how these birds work. Termed as scale –free correlation, it means that a bird within the flock will respond to the next individual’s movements and this will ripple across the entire group, regardless of size, at such a speed that it appears simultaneous.
Andrea Cavanga, a biological scientist based in Europe has headed up the research on this and has come up with interesting findings on the concept of scale-free correlation:
“Correlation is the expression of an indirect information transfer mediated by the direct interaction between the individuals: Two animals that are outside their range of direct interaction (be it visual, acoustic, hydrodynamic, or any other) may still be correlated if information is transferred from one to another through the intermediate interacting animals.”
He continues to explain how these behavioral correlations are what enable the group to “respond collectively to the environment”. The theory here goes that if one individual passes on a message to the other, the interaction is on a one to one basis yet the correlation of this message can continue along the line, as long as the information being passed along is good. In the case of these bird flocks there is no scale or seeming limit to this correlation, which is how this phenomenon has been referred to as scale-free correlation.
“The effective perception range of each individual is as large as the entire group and it becomes possible to transfer undamped information to all animals, no matter their distance, making the group respond as one.”
Another study suggests that the information being transferred happens between several individuals at once and not just on a one to one basis. This means that as these smaller groups are constantly communicating and overlapping, the information is passed on much faster resulting in instantaneous movements.
Reasons for this adaptation in this allelomimetic behaviour range from responses to predation, food location and migration. It would make sense in the case of red-billed quelea, which are known for localised migration in response to food resources. It is what makes them such a frustration to farmers who can lose an entire crop when a quelea flock moves through.
Although further studies continue in this field, what is so magical about this phenomenon is that it is not completely understood. That humans do not have a complete understanding of the intricacies of nature only adds to its wonder.
Written by: Andrea Campbell, Londolozi, LandCare Assistant
Have you ever seen a murmuration before?