From Liverpool Bay, a flock of mysterious sea birds disappears into the night

The Post's weekend read: A network of birders try to answer a decades-old question

By Harry Shukman

It’s twilight on April Fools Day last year, a week into the first lockdown. It’s cold — just a few degrees above freezing — and getting colder as the sun sets. Across the North West, a network of birdwatchers are testing their audio equipment and wrapping up warm. They are taking part in a sort of crowdsourced scientific experiment, conducted in their back gardens and designed to answer a question that has eluded ornithologists for decades.

One of the birders is Dan Gornall, a 25-year-old conservationist from Maghull, Sefton, who has been watching the skies since childhood. The stay-at-home order has frustrated his attempts to get out into the countryside and observe the wildlife. Like countless other birders, Dan needs an avian fix. So when he spots a tweet saying that flocks of common scoters are migrating east from Liverpool Bay, he puts on four layers of clothes, steps out into the dusk, and wriggles into a sleeping bag. He sits quietly and waits.

And then they come. Hundreds, maybe thousands of these mysterious sea ducks, fluttering right over his head, cheeping their nocturnal flight calls that tell the flock to stay together. They sound like delicate little laments, soft and sad cries in the dark. This is birding magic.

“To hear them going over your house at once was something amazing,” he says. “They pile over, all at the same time. It was quite hard to work out how many birds there were. I’ve been birding for about nine years now and it was completely new to me. Common scoters are quite a secretive species — one that you don’t hear.”

These birds are more interesting than their name suggests. The male scoter is as black as coal, but he’s got a fiery splash of orange on his bill. There’s a ring of the same colour around his eyes, a smear of disco mascara. The female has a head like a pair of two-tone spats — dark on top, white on the bottom. The bird is threatened, having lost 50% of its population in the last 20 years.

They spend most of the year, late summer through the winter, in Liverpool Bay. You can see them from the shore if you have a pair of binoculars. They occasionally show up on reservoirs and lakes but they prefer the sea. Out in the distance, they form a mush of black on the surface of the water, where they sleep and squawk and slurp up molluscs. A decade ago it was estimated that more than 50,000 of them — 58% of Britain's population — lived in the bay, one of the reasons why it has been designated as a Special Protection Area for birds.

Then one day in spring, as dusk starts to fall, the scoters take off. They disappear from Merseyside, swallowed by the night. Improbably, these small birds reappear in Scandinavia — deep with the Arctic Circle, as far north as Europe goes — having completed a migratory journey around 1,500 miles. For the short summer, they breed and have chicks before coming back — first the males, then the females, to Liverpool Bay.

Ornithologists have long wondered how they make the trip. Common scoters are pelagic birds, meaning they live on the open sea. So did they migrate over the tip of Scotland? Or south via the English Channel? Because the scoters set off at night, it’s hard to track them. But that changed last year, when the gradual proliferation of avian recording equipment, lockdown tedium, and mounting interest in the scoters created the ideal conditions to clear up some of the questions.

Noticing the birds were starting to migrate, a team of researchers at Manchester Metropolitan University shared requests in online birding communities to keep an ear out for them. The lively birdwatching groups of Twitter and WhatsApp answered the call. On a few spectacular nights in early April, hundreds of birders took out their audio devices and sat shivering in their back gardens for hours, taping the common scoter’s nocturnal flight call. The MMU researchers hoped to use the national network of birders — who were confined to their homes — to build a picture of where the common scoters were headed. Volunteers could submit audio recordings if they had equipment, or like Dan share their location if they heard the birds flying overhead.

Dan stayed out from sunset to midnight listening to the scoters. As the last ones flew by, he checked in with other birders online to see where the scoters had ended up. For the first time, the early stages of their migratory route had been mapped. Instead of flying over the Orkney Islands or south past Dover, they took a shortcut over the Peaks before heading out over the North Sea.

Dr Alex Lees, a researcher at MMU who has studied common scoters on and off for twenty years, was taken aback when he started to study the data provided by the amateur birders. “It shouldn't really come as a surprise because they are physically capable of flying over land but it shocked our perception of how these birds migrate,” he told me. “It was a great crowdsourced data set which revealed more about overland scoter migration in three days than we assembled in the previous hundred years.”

His call-out for common scoter sightings last year received 1,096 individual observations from 215 locations, most of which occurred over four days between March and April 2020. These data points form part of a research paper due out in the new year.

Alex and I met this week on the MMU campus. His practical clothing — anorak, comfortable shoes, bird-related baseball cap — suggest that he would be much more at ease setting up audio recording devices on a coastal nature reserve in the lashing rain than queuing for an Americano in the business school café. He has been watching birds since he could walk, and knows which tall buildings the local peregrine likes to hang out on top of.

The way he narrates some bird action happening nearby invites comparisons with David Attenborough. Migrant blackbirds are guzzling red berries on one of the trees and the instant that one of them emits a loud chirp, all the birds in the park fly off. “The alarm call,” says Alex. “The pigeons have gone up, reacting to the blackbirds. They’ve perceived danger. So it could be a peregrin? Often the first indication of seeing a bird of prey will be tuning in on the alarm calls of other birds.” There’s no sign of the predator, but it could be too high up for us to see.

In the common scoter study, Alex talks about how his team benefitted from the growing popularity of nocturnal migration observation, known as noc-migging. The cost of a Dictaphone is all it takes to participate. You can put the tape recorder on an outside windowsill at night and play it back the next day to hear different nocturnal flight calls. Alex says that some keen birders have dug trenches in the gardens to install parabolic dish recorders, or buy specialist devices that cost £1,000. His own set-up is a reinforced metal box with a recorder inside.

After a lifetime of birding, Alex, 41, has learned to recognise the scramble of audio lines on his computer screen as individual bird calls, so he can quickly scroll through the visualisation of last night’s recording to see who was singing. “I can also recognise a dog barking in a car, or a siren going past,” he adds. Part of the appeal of noc-migging is that nocturnal flight calls are comparatively understudied, allowing birders to break new ground in research. “It shows how little we know about the avifauna of one of the best studied countries in the world,” says Alex, referring to avian fauna. “You can still make some exciting discoveries.”

Understanding the common scoter’s migration route can help with conservation. If researchers can identify the bird’s stopover sites — estuaries, for instance — then they can be protected. Studying the amounts of disruptive artificial light on the scoter’s nighttime route, as well as the building infrastructure that could get in the way, might yield clues to help stop the bird’s population from dwindling further.

Some of the scoters from Liverpool Bay have a staging post in North Norfolk, where Alex remembers seeing them as a boy, before they set off for the Skagerrak — the strait separating Denmark from Norway — then the Baltic Sea, and finally northern Scandinavia.

Had the lockdown not happened, keeping a lot of birders inside with nothing to do, then the common scoter’s migration route could still be a mystery. “There is something existentially special about sitting in your garden listening to hundreds of sea ducks flying over in the dead of the night,” says Alex. “It’s a surreal wildlife experience, and all the better for being able to turn it into a scientific story.”

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