Starling Murmurations in Galloway

This blog is amended from an article originally written in 2019 for the RSPB Galloway newsletter

We’re privileged in Galloway to be able to enjoy one of nature’s most impressive displays, performed at dusk in the winter months by our very own resident starlings, assisted by seasonal reinforcements from Europe. Murmurations are the close formation flying of very large numbers of starlings, as they gather from a wide area and prepare to shelter in a communal roost. The shapes and patterns which they form in the sky can be mesmerizing to watch, prompting numerous questions as to how and why the birds behave in this way, and offering insights into other fields where the emergent behaviour of a large cluster of animals, people or inanimate objects would not be easily predicted from observations of a small number of individuals.

A murmuration above Carlingwark Loch, and a Castle Douglas starling.

Attempts to explain starling murmurations aren’t new. Pliny the Elder, in one of his less bizarre deductions, declared that each starling in the ball shaped formation was seeking to reach the centre of the ball. Two thousand years later, one of the most cited scientific papers on starling murmurations describes a study which deployed high-speed stereo cameras at Rome’s main railway station. Given the consummate sky dancing of the study’s subject, it’s wonderfully appropriate that the lead author’s name is Ballerini. He and his team concluded that each bird in the formation manoeuvres and avoids collisions by noting the positions of only its nearest six or seven neighbours, regardless of their distance. Not all citizens of Rome appreciate their free flying display. If a single starling produces up to 50g of guano each day, the effect of several million starlings is easy to imagine. Italians have a word for it, and several gestures.

Small groups of birds moving in different directions form more or less motion blur in the image when the camera is panned during the exposure. Starlings moving from the reeds at Mersehead into the trees appear like iron filings in a magnetic field.

Closer to home, Daniel Pearce and his colleagues at the University of Warwick developed a computer simulation with good correspondence to observations of starling murmurations. In their model, the projected view of each bird to the outside of the formation is marginally opaque, so that every bird can see out in many directions, and this condition is maintained by each bird being attracted to an aggregate direction of all the light/dark boundaries in its field of vision. The property of marginal opacity allows the approach of a predator to be detected by most birds at the same time, and also permits an outside observer to see right through most parts of the formation, as can be seen in the murmurations of our Galloway birds.

It's easy to see why Pliny the Elder thought that the birds were attempting to make the shape of a ball, but the marginal opacity hypothesis is probably more convincing today.

By deploying ‘citizen scientists’ mostly within the United Kingdom, Anne Goodenough at the University of Gloucestershire, and her colleagues obtained detailed descriptions of over 3000 murmurations, including several in Galloway. Correlations in their very large data set allowed them to conclude that murmurations are more likely to be an anti-predator mechanism, rather than a means of attracting large numbers of starlings together for improved energy efficiency within a larger roost.

A murmuration above Whitepark, Castle Douglas, and a squadron at Laurieston on their way to the main rendezvous.

Here in Galloway, we have an advantage over the people of Rome, because our starlings can easily be seen in more rural locations, without our having to stand directly beneath them. The RSPB reserve at Mersehead often has murmurations of tens of thousands of starlings, easily viewed from the Meida Hide, and there are often good displays in and around Castle Douglas, where I have seen several impressive starling responses to threats from sparrowhawk and red kite. So, wrap up warmly, and enjoy the show.

A starling tornado, and a bird which may have taken part in the display.

References

Ballerini et al. (2008) Interaction ruling animal collective behavior depends on topological rather than metric distance: Evidence from a field study
Goodenough et al. (2017) Birds of a feather flock together: Insights into starling murmuration behaviour revealed using citizen science
Pearce et al (2014) Role of projection in the control of bird flocks