Falcons do go after tightly packed crowds of dunlins and other shorebirds, but those hunts are most likely to succeed when the attack causes a solo bird to stray. Studies have shown that merlins hunting shorebirds are in fact most successful when they’re pursuing individuals. By turning rapidly or simply tilting a bit on their axis, dunlins are able to shift the appearance of their plumage from dark (their upperparts) to light (their underparts), creating a swift flashing effect that might startle or confuse predators. That’s due in no small part to the bewildering things that an assemblage can do. Numerous studies have shown that individuals that travel in groups are almost always more vulnerable when they stray off by themselves. It’s when a predator lunges, though, that being in a crowd really pays off. More eyes and ears mean increased opportunities to find food and improved chances of detecting a predator in time. On one level it has long been obvious what’s going on when animals synchronize their movements-be they ducks, wildebeest, herring, or social insects. “There’s a lot we don’t know now,” says Heppner, “but I think we’re actually going to know how and why birds fly in organized groups within five years.” As a result, researchers are closer than ever to really getting inside the mind of the flock. So has a new wave of interest from other scientists, including mathematicians, physicists, even economists. Today, though, technological innovations, from high-speed photography to computer simulations, have enabled biologists to view and analyze bird flocks as never before. “The fact that we weren’t hooted out of town is an indication of how desperate we were to explain this stuff,” he says now.
When Heppner, now semi-retired, began studying pigeon flocks more than 30 years ago, he suggested that they communicate through some sort of neurologically based “biological radio.” No wonder observers have been left groping for an explanation.
#Flocks of geese drivers#
Imagine doing unrehearsed evasive maneuvers in concert with all the other fast-moving drivers around you on an expressway, and you get an idea of the difficulty involved. Yet they can make astonishingly sharp turns that appear, to the unaided eye, to be conducted entirely in unison. They often fly at speeds of 40 miles or more per hour, and in a dense group the space between them may be only a bit more than their body length. But the most impressive flockers are arguably those that form large, irregularly shaped masses, such as starlings, shorebirds, and blackbirds. Pelicans, geese, and other waterfowl form lines and Vs, presumably to take advantage of aerodynamic factors that save energy. But only a relative handful really fly together, creating what University of Rhode Island biologist Frank Heppner, in the 1970s, proposed calling “flight flocks”: namely, highly organized lines or clusters. See this article's accompanying photo gallery
What else can it be?” mused one British naturalist, rather plaintively, in 1931. Scientists of the early 20th century, perhaps almost as credulous, groped for such mysterious and even mystical concepts as “natural telepathy” or a “group soul.” “It is transfused thought, thought transference-collective thinking practically.
The ancient Romans had their explanation: Gods, they believed, hinted at their intentions in the way birds flew. Since primeval times people have looked at masses of birds moving as one and wondered how they do it. A distant murmuration of starlings-and yes, that really is the marvelous term for a group of these often-maligned birds-10,000 or more, rolls “like a drunken fingerprint across the sky,” as the poet Richard Wilbur wrote, smudging the dusk horizon with the quickness of a pulsating jellyfish. A dark flock of dunlins sprints straight over a marsh-until a merlin appears and they all veer at the same moment, flashing their bright white underparts and rearranging their group into an hourglass shape with shocking swiftness.
0 kommentar(er)
