Why Do Starlings Murmurate? Predators, Warmth & Safety
Starlings murmurate mainly for safety in numbers: a dense, shifting flock is very hard for a predator to attack. Gathering at dusk before they roost may also help the birds stay warm through cold nights and swap information about where to feed the next day. Most likely these benefits overlap, and the anti-predator advantage is the one with the strongest evidence behind it.
Safety in numbers
The most widely supported reason is defense. As the RSPB puts it, flying together “creating a moving mass of birds” lets starlings “confuse potential predatory species and make it harder for them to pick off individual birds.”
The threat is real. Murmurations frequently form where birds of prey such as peregrine falcons and sparrowhawks are hunting. For a predator, a lone starling is an easy meal, but a churning cloud of tens of thousands is a nightmare: the constant motion makes it hard to fix on a single target, and diving into the mass risks injury. This is often called the “confusion effect,” and it is the leading explanation for why the birds go to the trouble of performing at all.
A large citizen-science study backs this up. In PLOS ONE (2017), Goodenough and colleagues analyzed more than 3,000 public murmuration reports and found the observations fit the anti-predator “safer together” hypothesis better than the idea that murmurations are primarily about keeping warm.
Warmth and shared information
That does not mean warmth plays no role. The RSPB notes that gathering at dusk before roosting also gives starlings “warmth and the opportunity to share information about the best feeding grounds.” Packing into a communal roost on a winter night can help conserve body heat, and joining a large roost may let a hungry bird follow well-fed neighbors to good food the next morning, a so-called “information center” benefit.
The 2017 citizen-science analysis found weaker support for warmth as the main driver than for predator defense, but these explanations are not mutually exclusive. A behavior can serve several purposes at once, and the pre-roost display may deliver a bit of each.
An honest amount of mystery
Scientists are refreshingly candid that murmurations are not fully solved. Why the display lasts so long, why some evenings produce spectacular formations and others almost none, and how much each benefit contributes are still active questions. Part of the enduring fascination is precisely that a behavior this visible still keeps a little of its secret.
What is clear is the mechanism underneath. The birds achieve these life-saving formations with no leader at all, each one tracking just its nearest neighbors, as we explain in how starlings fly without colliding and in the full science of the murmuration.
If the calm of watching that motion appeals to you, it belongs to the same family of quiet, screen-based relaxation we cover in what ASMR is.
Frequently asked questions
Why do starlings murmurate? The leading explanation is safety in numbers. A dense, swirling flock makes it hard for a predator to target any single bird. Gathering at dusk before roosting may also help starlings keep warm and share information about good feeding grounds.
What predators are murmurations defending against? Birds of prey such as peregrine falcons and sparrowhawks. Attacking a fast, constantly shifting mass of thousands of birds is far harder than picking off a lone straggler.
Do scientists fully understand why murmurations happen? The anti-predator explanation has the strongest evidence, but researchers are open that the behavior is not completely solved. Several benefits likely overlap, and some questions remain open.