Birds that were flying abreast are now flying one behind the other. This means that the positions of birds relative to one another change after making a 90-degree turn. This enables fish to maintain their original spot in the group and keeps the school elongated.īirds in a flock, however, turn individually, as is shown in observations of circling rock pigeons published by American biologists Harold Pomeroy and Frank Heppner in 1992. According to the models and empirical research conducted by Hemelrijk's group, individual fish on the outside of a turning group are able to accelerate slightly, while those on the inside slow down. The turning probably happens differently in birds and in fish. Whenever starlings in the model left the area above the sleeping site they were made to turn back. The program was used to simulate how flocks of starlings circle above a roosting place. ![]() The simulated starlings experience a lifting force, drag and gravity, and bank when turning. In addition, the model contains mathematical functions describing the flying behaviour using simplified aerodynamics. The new StarDisplay model was once again based on a limited number of principles: birds are attracted to each other, they move in the same direction and they try to avoid bumping into one another. "We wanted to find out whether self-organization could provide an adequate explanation," Hemelrijk states. In the 1930s, British ornithologist Edmund Selous - also fascinated by flocks - even attributed the tremendous variety to telepathy. People have wondered for ages how all these different shapes are able to be created. Round, broad, elongated, flocks that shift shape from funnels to hourglasses, thickening, thinning these are all existing variations. Video footage of flocks of starlings flying around in search of a place to roost show fantastic variation all over the world. This results in an elongated school.įlocks of starlings, however, produce a much richer variety of shapes. A fish swimming behind another one will slow down to avoid bumping into the one ahead of it and its former neighbours then move inwards to fill the gap that has opened up. ![]() In addition to the usual grouping and coordination, no extra rules are needed to achieve this. "Our models showed that the elongated shape of schools of fish were the automatic result of self-organization," Hemelrijk says. Observations in nature showed that these are always elongated. Previously, Hemelrijk and her collaborators used a comparable computer model to investigate schools of fish. In an article in the online journal PLoS ONE, Hemelrijk and scientific programmer Hanno Hildenbrandt use the StarDisplay computer model to describe the causes of the miraculous variety of shapes in flocks of starlings.
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