A murmuration of starlings

Murmuration is my new a favourite word, it means a flock of starlings. It is one of the old English collective nouns for a group of animals, like a murder of crows, a skulk of foxes or a gaggle of geese. And as the YouTube clip above shows murmurations are simply astonishing.  The Guardian also has a gallery with some pretty amazing pictures. Thousands of starlings flying through the air as if they were a single organism. Flicking back and fore like cat’s tail, not like the thousands of bird spread across maybe 100 m that they are.

These amazing aerial displays are quite common near sunset, and we don’t really know why they do it or how the thousands of birds achieve such incredible synchronisation. But Cavagna et al. observed murmurations of between a few hundred and a few thousand starlings in evenings at the Palazzo Massimo in Rome. As an aside, I’d like to say that observing beautiful aerial displays in an Italian Palazzo sounds like a pretty fantastic job.

I really like Cavagna et al.s paper. They study the correlations between the motion of murmurations of up to a few thousand starlings. They show that both the speed and the direction of flying of the starlings are very strongly correlated. A starling at one end of the murmuration is flying in lock step with one at the other end — the murmuration is almost flying like a rigid object. So when in the clip above the murmuration is changing direction it is almost like a rigid object rotating — only the object is just a cloud of starlings.

Remarkably, this is true however big the murmuration is, i.e., it is as true for the largest murmuration as for the smallest. This begs the question of how a starling manages to fly in lock step with another starling 100 m away. We don’t know the answer to this question. Either starlings can somehow directly determine accurately the direction the whole murmuration is going in, or each starling can determine how its neighbours are moving so accurately then when this information can be passed from starling to starling across the whole murmuration.

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