The sight of thousands of starlings swirling and spinning through the winter sky is one of nature’s true wonders. Naturalist and bestselling author Stephen Moss leads us into the Somerset Levels for front row seats

A large crowd has gathered in the shadow of Glastonbury Tor, an hour or so before dusk on a chilly winter’s evening. The congregation of 500 or more prepare quietly, yet with a frisson of excitement, for the forthcoming act of worship. But they are not here to pay homage to the pagan gods of ancient Avalon, nor the more conventional religion practised in nearby Wells Cathedral. Instead they have come to the heart of the Somerset Levels to witness one of the greatest of all wildlife spectacles on the planet: the jaw-dropping display of a quarter of a million starlings gathering as they come to roost.

For many it is their first experience of this avian phenomenon. For me, it is perhaps the hundredth time I have made the pilgrimage in the decade since I first moved down from London to Somerset. Yet however many times I watch these birds flocking together to perform their extraordinary sky dances, it never fails to astound me.

As we wait in anticipation, a young man approaches and asks me where would be the best place for him to stand to witness the spectacle. I tell him that we’re hoping the starlings will come down in the reedbed just in front of us, but that – as with any natural event – there are no guarantees. I have been here on some nights when the flocks have flown right over our heads, but instead of landing, they have carried on another mile or so to roost at the other end of these vast marshes. Once – and only once, on Boxing Day a year ago – we hardly saw a single bird. That night they must have suddenly chosen, for no apparent reason, to head to a completely different place.

Despite these caveats, I am hopeful tonight. The weather is perfect: cold, with no hint of a breeze, and bright, promising a lovely sunset just behind where the birds will land. And so we wait. And wait. A flock of black-headed gulls appears, prompting the less ornithological among the crowd to utter a yell of excitement that quickly transforms into a cough. Then little egrets fly across the reeds, Persil-white and impossibly elegant, followed by a much larger all-white bird.

A few years ago my son Charlie saw one of these, and called out: ‘Daddy! Great white!’ This caused a small panic among the gathering, as some wondered if the world’s most dangerous predator was lurking in the shallow waters in front of us. Then fear turned to relieved laughter as it dawned on them that this huge bird was actually a great white egret, not a shark.

With about 20 minutes to go before sunset, the crowd is getting restless. They begin to chat among themselves, becoming so distracted that when the first flock of a thousand or so starlings flies right over our heads, they miss them. Fortunately, the RSPB’s volunteer wardens are on hand to point out the birds. The curtain is drawn and the show has begun.

For the next half hour, the event builds towards its climax. First, small flocks appear from all four corners of the compass, making a whooshing sound as the air ruffles their wings, which is the reason a large gathering of starlings is known as a murmuration. As they reach the reedbed, some fly straight over, while others begin to gather in larger and larger flocks.

For first-time viewers, this is exciting enough, as the gasps and squeals of delight bear witness. But old hands know that this is simply the overture to the main event. The performance does not always go to plan, though: some evenings the birds arrive and decide to plunge right down into the reeds almost straight away where they will spend the night, leaving the crowds hungry for more.

But tonight, I have a good feeling. And my faith is justified. In the distance, a vast cloud of what at first looks like smoke crystallises into a flock of starlings. As they come nearer, they move closer and closer together, until they form a huge black cloud, right above the reedbed. We’re into the main act now. The cloud reforms into a tall tower, before – without any warning – shape-shifting in the skies above our heads. Over the next few minutes we enjoy a classic series of ‘wow’ moments, as the starling flock behaves like a single organism, swirling and spinning, eddying and churning, rolling and blending. The watchers are ecstatic; I am simply relieved.

Then, as the sun finally falls below the horizon, and the sky begins to darken, the birds go to roost. It is as if someone has pulled the plug out of a tub of swirling water. A stream of black pours straight down into the reeds, as the sky above empties of birds. A tipping point has been passed, and the birds’ only imperative now is to find a safe place to spend the night.

Next, the noise. While airborne, starlings do not call at all; but as soon as they have landed in the reeds they start to chatter. At first this is hardly audible above the buzz of the watching crowd; but within a few minutes the sound of the birds drowns out their voices, and the people fall silent. Scanning with my binoculars, I can see individual starlings jostling for position; when I look with the naked eye all I can see is a long strip of black obscuring the pale colour of the reeds.

Then darkness finally falls, and the show is over. The crowd disperses, excitedly recalling the high points of the evening. I linger behind. Even though it is too dark for me to see, I can still hear the cacophony of starlings as they settle down to sleep.

So why do starlings gather in such huge flocks on winter evenings? The simple answer is that there is safety in numbers. If these birds chose to spend the night on their own or in smaller flocks, they could be vulnerable to predators such as peregrine falcons and sparrowhawks.

You might think that these hunters would welcome an even bigger gathering but, in fact, they struggle to target individual birds in such a huge mass, and often give up the chase. This means that for each individual starling, the chances of being taken by a predator are far lower if they join forces with their fellows. They can also stay much warmer. Keeping up their energy levels is crucial at this time of year, and by spending the night huddled with their neighbours in a vast reedbed the birds can ensure that they retain precious heat.

Finally, they use the roost to communicate with one another. Although they appear to be ‘chatting’, what they are actually doing is far subtler. Any starling that has not been able to find enough food that day will seek out the healthiest looking starlings, which have. The next morning, they stick close to those birds and so get to find the best places to feed.

Another big question is, why do starlings perform such spectacular aerial dances? This is trickier to answer as it involves pretty complex mathematics and the science of crowd behaviour. We all know that as individuals we behave differently when we are in a crowd – the simple fact of being among a big group of people means we tend to follow those closest to us. The starlings are exactly the same: each individual is trying its best to stick as close as possible to the birds around them. So when one bird on the edge of the flock spots a predator, and turns to avoid it, those around it also turn – but do so a split-second later. To the watchers, it looks as if the flock has developed a mind of its own, as it forms new patterns and shapes in the sky.

The reason the flock stays airborne for so long – wasting precious energy in flight – is also fairly straightforward. The first birds to leave the flock and plummet into the reeds may get the best place to roost for the night, but they also expose themselves to danger, by leaving the safe haven of the crowd. So the starlings weave about just above the reeds, until as the sky darkens, enough of them decide it’s time to head down. At that point there is a mad rush not to get left behind, and the birds descend as rapidly as they can.

Starlings have always come together in huge flocks like this on winter evenings. Indeed, when I was growing up in the 1970s they were a far more frequent sight. I recall seeing – and hearing – them in London’s Leicester Square, where they would gather on the window ledges of buildings, outcompeting the sounds of the city with their calls.

When we drove back home after a day in the countryside, we would often come across vast flocks of starlings, swirling up from the fields or over woods as dusk began to fall. Later, in the early 1980s, I saw them gathering around Chelsea Bridge in west London, and over the vast Victorian edifice of Bristol’s Temple Meads railway station. And on a visit to the Sussex seaside resort of Brighton in the 1990s, I watched entranced as flocks of starlings swirled around the famous West Pier.

Now all these roosts have gone, apart from the one in Brighton, which when the West Pier was destroyed by fire moved a few hundred yards along the beach to the Palace Pier. Even the roost I am watching here in Somerset is a shadow of what it once was: locals claim that there used to be seven million birds here; though I suspect the number was more like one or two million. Today it’s around 250,000 starlings gathering each evening – still a very impressive sight and the largest remaining roost in Britain.

There are two reasons why starling numbers are down. First, like other birds that depend on farmland, they are suffering from the move towards highly intensive, chemical-driven agriculture, which turns our countryside into a food factory and leaves little or no room for wildlife. The other reason is that many of the starlings I am watching tonight come from eastern Europe and Russia, where the intensification
of farming has also led to big reductions in starling numbers.

The morning after our night show, we gather again. It is a bone-cold dawn, but bright and clear. There are far fewer of us than before: maybe half-a-dozen dedicated souls. But it’s well worth it. As the sky starts to lighten over the famous tor, the birds begin to utter their orchestra of sound. Then, at some unseen signal, they rise as one into the air and head away in a long black stream, out into the fields and marshes of Somerset to feed.

One of the reasons for the popularity of the starling spectacular is a TV programme I made with Bill Oddie around the turn of the millennium at a roost near Slimbridge in Gloucestershire. That night the birds performed brilliantly, and despite having watched birds for more than half a century, Bill was almost speechless with awe. He still refers to it as our ‘Hey Jude’ moment – the greatest of our greatest hits. The footage was even bought by a famous brand of lager to advertise ‘togetherness’. But I’d say that the starling roost near my home on the Somerset Levels is probably the best starling roost in the world. Nights and mornings like this are something I think everyone should experience.

This story originally appeared in Postcard, a bi-annual, in-room print magazine which UNTOLD created for Best Western Hotels