Why do birds fly together in large groups?

Updated November 21, 2016

Birds swooping overhead in unison, swiftly dodging predators and escaping harm, leave watchers awestruck and dazzled. The synchronicity and speed at which these birds move together amazes commoners and scientists. Researchers are beginning to learn more about why birds fly in groups, but there are questions that remain unanswered. Group flight patterns suggest that birds fly together to avoid predators, for socialisation, to optimise flight and energy conservation, and to avoid accidents and collisions.

Survival of the Most Adept

Studies show that birds learn to fly in flocks over time, gaining speed and agility. Mastering the quick movements and keeping up with the group takes practice, and stragglers are the most vulnerable to predator attacks. Many scientists believe this is the strength of the group dynamic; the whole is greater than the sum of its parts. While one bird may fall victim, most of the group is safe.

Eluding Predators

Flocks create tight formations and move swiftly to avoid predators. When dunlins turn quickly they reveal their underparts, a lighter plumage, contrasting with the darker plumage of their upperparts. This creates a flashing effect, distracting and startling predators. Claudio Carere, an Italian ornithologist, makes observations about starling flocks. Falcons lurk and attack starlings as they approach the roosts. "They compact and decompact, split and merge, form 'terror waves,'" moving away from a falcon in a split second. Predators may also get hurt diving into a large group that is moving continuously in different directions.

Socialisation & Hierarchy

Studies show that flocks work best and are tranquil when every bird knows its place, humbly flying in unison. A recent U.K. study observed leadership in pigeon flocks. Dora Biro of the University of Oxford and her colleagues put GPS backpacks on the pigeons to ascertain which pigeon was leading the group. The study revealed that some birds had more birds following them, and these birds flew closer to the front. "You can actually rank birds in terms of the influence that they have on others within the group," Biro says.

Aerodynamic Factors & Energy Conservation

A well-organised flock is efficient, taking advantage of the increased aerodynamic factors of group flight versus individual flight. Migratory configurations not only offer safety in numbers, but also optimise flight and conserve energy. "V" formations, for example, offer decreased drag. It is possible this decrease in fatigue increases chances of survival.

Finding Food

Increased numbers offer better chances of finding food. Studies show that individual birds learn from each other, following other birds to find food. This is seen in various species, such as ospreys and swallows.

Multispecies flocks

Multispecies flocks normally include small groups of various species. It offers the same safety in numbers, but also allows for shared resources among species. Considering the decrease in natural habitat for all wildlife due to human encroachment, it is a necessary survival tactic.

Still a Mystery

How bird flocks move so quickly remains a mystery, as well as how they coordinate such synchronised, diverse, abrupt and complicated movements. Some say it's by watching neighbours and following along, but the reaction is so quick it seems there is something else going on. Scientists in the early 1900s hypothesised telepathy or some type of group soul. Frank Heppner also noticed that Roman starlings will swirl, making grand swooping motions before settling down in their nests. Wouldn't this attract predators? So despite years of research and observation, birds' motivations continually elude us, much as they elude their predators.

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