NIGHT BIRDS OF MOUSA

A summer’s night on a windswept island and a strange wildlife spectacle is about to begin. James Fair meets the tiny storm petrels of Mousa island.

A summer night in the North Atlantic and one of Britain’s strangest wildlife spectacles is about to begin. On a treeless, windswept island, James Fair watches small and secretive creatures emerge to flock around an ancient ruin...

It is night-time on the isle of Mousa, but while the clock has crept well past 11pm, it’s not yet dark. At this time of year, so far north – this small island off the coast of Mainland Shetland is on the same latitude as Stockholm – night-time is a relative concept. Locals call these twilight nights “da simmer dim”. Yet stranger and more magical is the sound issuing from the rocks by my knees: a soothing churr that ends in a breathy hiccup and then repeats on an endless, hypnotic loop.

I had come across by boat from Sandsayre Wick, with a group of other sightseers. Before we were let loose on the island, we had been given a stern lecture on the fragility of this environment and the potential risk we pose to the wildlife, so after lingering a while longer, I reluctantly move on. Mousa is tiny and treeless, so the sight of an obviously ancient building towering at the water’s edge is startling. The broch of Mousa is 2,000 years old and rises 13 metres from the ground. It was probably built either as a place to live or as a fortification against invaders; no one knows for sure (see page 50). Tonight its slightly concave drystone walls are subtly silhouetted against the inky-blue sky. The 30 or 40 people who arrived with me are now sitting around the broch in small, quiet groups, soaking up the sense of place and time and history.

And they’re watching the walls of the broch, because from a few metres away, you can clearly see there are animals fluttering around it resembling dark, gothic butterflies. If I were anywhere but Mousa, or a handful of other islands around the coast of Britain, I would assume they were bats. They’re bat-sized and it’s night-time. What else could they be? They’re clearly not owls. Moving closer, I can hear that strange hypnotic sound again, but bats don’t churr and hiccup like this, to the best

of my knowledge. The noise has famously been described as sounding like a fairy being sick.

BRAVEHEART BIRDS

They’re not fairies, of course, but European storm petrels, sparrow-sized seabirds so heroic and hardy they make Ernest Shackleton look like a Sunday morning rambler. They’re returning under the cover of whatever darkness there is – on clear nights with a full moon they don’t come back at all – to their nests, which they make either under natural boulders or in the walls of the broch. An estimated 11,000 pairs breed on the island, with roughly 400 using the broch, making it surely the UK’s largest and most remarkable nestbox.

That hypnotic churring sound is the sound of their mates. The returning birds use a combination of that and their sense of smell to find their partners, who have either been sitting on a single egg or tending to the chick.

Kevin Kelly, of the RSPB, which manages Mousa on behalf of the island’s owner, tells me he took a crew from National Geographic out to film the storm petrels last year and says the footage was amazing. “You could see them attempting a fly-past – ‘is that the right hole, is that it?’ They flutter around, then go on and come back,” he says. “We even managed to film them inside the nest [in the broch] and saw

them re-establishing their pair bonds after one of them has been out at sea fishing.”

But why all the subterfuge? Why come back like thieves in the night, when seabirds such as puffins, guillemots and razorbills quite happily come and go all day long? Well, not only are storm petrels tiny – a perfect snack for predatory birds, such as great and lesser black-backed gulls and menacing great and Arctic skuas – they are also, like shearwaters, surprisingly badly adapted to life on land.

Their feet are set far back on their bodies, and this anatomical adaptation enables them to quite literally walk on water – it’s where they get their name (see box, left) – and this is how they

feed, scooping up tiny fish and plankton from the surface. But it also makes them ridiculously clumsy on land.

I’ve never seen a storm petrel walk, but on the island of Skomer off West Wales I’ve watched shearwaters wander about like drunks. They make a good meal for the blackbacked gulls that sit around in thuggishlooking gangs. The desiccated remains – quite often just a pair of wings – of those that made the mistake of returning when it wasn’t quite dark litter the island, a reminder of the deadly perils they face.

INTREPID TRAVELLERS

Once the handover between mates is complete, the bird that has been confined to the nest can now escape for a day or two to feed. Some may just go for the night, flying a relatively short distance, while others have been recorded travelling up to 300km in search of food.

Some time in September, the single chick will fledge, then they will all head out into the North Atlantic and down to the coast of South Africa for the winter, an epic journey of some 12,000km. Indeed, these tiny birds weighing just 30 grams – the equivalent of just three or four cherry tomatoes – spend more than half their lives out at sea, frequently buffeted by

gale-force winds. Hardy and heroic doesn’t begin to do them justice.

I wander inside the broch, which is so well preserved it even has a functional staircase (making it the oldest one in Britain, I’m told). I walk to the top, listening out for petrels nesting under the stairs and in the walls as I go, and sit on a small flat area looking out over the island.

By now, it’s midnight. During the day, the boulder beach at West Pool – a short distance from the broch on the other side of the island – is alive with the calls of Arctic terns and fly-pasts from skuas. Common seals – ironically, the less common of the two seal species regularly found in UK waters – are pupping, too. But only the petrels are active at this time of night.

Meanwhile, the water in the sound between Mousa and the mainland is visible, with everything cast in a soft blue cloak. Occasionally, a fluttering form will rise up above the level of the wall, then dive back down as it homes in on its partner. But with the dawn of a new day just hours away, the crew of the Solan IV want to head back to the mainland, and they round us up like sheep for the short passage across the sound. It feels about time.

Under the cover of darkness, a European storm petrel – Britain’s smallest seabird, only a little bigger than a sparrow – finds the right nesting hole, and moves in to greet its partner. These delicate birds lay only one egg a year and the male and female take turns sitting on the nest, for 38–50 days of incubation

Now uninhabited, Mousa was populated from the Bronze Age to the mid-19th century. The Haa or laird’s house was built near the broch in 1783 for Lerwick merchant John Pyper, who bought the island. His widow lived there until her death in 1852

ABOVE Storm petrels – with their distinctive white patch on the rump – choose high nesting spots to protect them from predatory mammals, including rats and mice ABOVE Inside the beautifully constructed drystone broch of Mousa, historian Vinnie Butler explains the history of this well-preserved 13m-high roundhouse, thought to have been built around 300BC

ABOVE Storm petrels’ scientific name, Hydrobates pelagicus, roughly translates as ‘to step on water on the sea’ – their feet flutter on the surface as they feed without alighting, dining on plankton, small fish and crustaceons

James Fair is an experienced wildlife journalist with a longstanding passion for the environment. He specialises in investigating controversial issues such as badger culling and the illegal wildlife trade.