A large group of birds flying in circles is most likely a murmuration of starlings. Murmurations are large flocks of starlings that fly in swooping, intricately coordinated patterns through the sky. This phenomenon occurs when starlings gather in huge numbers, up to tens or hundreds of thousands of birds, to roost for the night. The coordinated movements of the flock are believed to serve as a defense mechanism against predators.
What is a murmuration?
A murmuration refers specifically to a flock of starlings flying in an aerial display. The term can also be used generally to refer to a large flock of any bird flying together in coordinated patterns. However, the most spectacular natural murmurations are formed by European starlings.
Murmurations consist of hundreds, thousands, upwards of a million starlings flying together in swooping, swirling patterns across the sky. The flock appears to move as a single coordinated unit, morphing its shape and direction in hypnotizing arrangements.
Starlings join in these aerial ballets when gathering to roost for the night. They congregate in the largest numbers over their winter roosting sites, where they may gather from miles around to create immense flocks.
When and where do murmurations occur?
Murmurations begin forming about an hour before sunset, as starlings start flocking back to their roosting site for the night. Popular roosting spots include reed beds or other dense vegetation that provides shelter, as well as urban structures like bridges, piers, and cliffs.
The greatest numbers of starlings, and thus the most spectacular murmurations, tend to gather in winter roosting sites from November to early March. However, smaller murmurations can be observed year-round as starlings gather in the evenings at both winter and summer roost sites.
The best places to witness murmurations are open areas near large roosting sites. Famous murmuration viewing spots include:
- Gretna Green in Scotland
- Westhay Moor Nature Reserve in Somerset, England
- Pier at Aberystwyth in Wales
- Rome city center in Italy
- Jasper Pulaski State Fish & Wildlife Area in Indiana, United States
What do murmurations look like?
Murmurations take on different shapes as they twist and turn through the sky. Common patterns include:
- Vortex: a circular swirling pattern, with a hollow center around which the birds revolve.
- Wave: an undulating wave-like form as part of the flock dips and rises.
- Blob: a shapeless amoeba-like cluster.
- Column: a tall cylinder shape as birds fly stacked vertically.
- Ballet: parts of the flock dance in weaving ribbons across the sky.
The speed and fluidity of their movements are remarkable considering the huge numbers of birds composing a single flock. Murmurations can spread for miles across the sky, yet still maneuver in astonishing unison.
Why do starlings create murmurations?
The main purpose of murmurations is thought to be for safety in numbers. When starlings band together in massive swarms, they can coordinate movements to confuse and avoid predators. Here are some of the leading theories on why starlings form murmurations:
Predator protection
Forming an immense flock provides safety through dilution. In a tightly-woven murmuration, it becomes difficult for a predator to track and catch any individual bird. It also allows the many eyes of the flock to watch for danger in all directions. Any movements by a predator can signal the entire flock to change direction in a synchronized wave.
Social coordination
Flying in a massive group may also make navigation easier. Each bird needs only mimic the motions of its closest neighbors to participate in the flock’s overall directional choices. This is known as swarm intelligence.
Information sharing
The constant proximity within a murmuration allows birds to share information. For example, experienced birds may lead new arrivals to good feeding grounds from the roost site.
Temperature regulation
Huddling together in a moving mass may help starlings stay warm through the winter nights. The density of birds within a murmuration traps heat at the center. Individuals can cycle through warmer and cooler areas of the flock.
Strength in numbers
There is safety in the immense size of a murmuration, making it an intimidating sight for predators. Banding together may also help starlings stake claim to a roosting site, seeing off other species like pigeons or crows.
How do starlings coordinate murmuration movements?
Researchers still do not fully understand how starlings coordinate their movements so precisely during murmurations. Here are some of the mechanisms they may use:
Mimicry
Starlings seem to closely match the actions of their nearest 6-7 neighbors while flying. This simple behavior spreads throughout the flock, allowing waves of movement to travel across huge numbers.
Vision
Starlings have incredible vision and can see ultraviolet light. Their eyes may allow them to coordinate visually with the intricate maneuvers of those around them.
Visual field range | Almost 360 degrees around their heads |
Number of photoreceptor cones | 4 – allowing tetrachromatic vision |
Synchronized movements
Physics research shows starlings in a flock will synchronize tiny adjustments in speed and direction with their neighbors. Matching the actions of those closest essentially allows changes to ripple through the flock.
Leadership
Experienced starlings that know good feeding areas and roost sites may act as leaders in starting murmuration movements. Their initial dives, turns or climbs can be amplified into flock-wide maneuvers.
Fun Facts About Murmurations
Here are some fun additional facts about starling murmurations:
- The longest recorded murmuration spanned over 80 miles across the sky.
- Density can reach up to 40 birds per cubic meter at the flock’s center.
- Young starlings join flocks and learn patterns through mimicry of those around them.
- Collisions are extremely rare due to precise flock coordination.
- Predators like peregrine falcons will hunt murmurations for an easy meal.
- Other birds like fieldfares may mix into the flocks.
- Murmurations gradually break up as starlings settle into the roost for the night.
Conclusion
In summary, a large group of birds flying in circular patterns is called a murmuration. These mesmerizing aerial displays are created by thousands of starlings flocking together to roost for the night. The leading theories suggest starlings form murmurations for safety benefits through uniting as a massive synchronized flock. Researchers continue working to further understand the complex coordination involved in creating these swirling patterns that grace the dusk skies over winter roosting grounds. Witnessing a murmuration firsthand is an unforgettable experience.