EVERY autumn for 30 years Angus Maciver has maintained a devoted vigil on the fringes of a bleak plateau, patiently waiting for the first glimpse of one of Scotland’s rarest visitors.

At 81 years old, he now prefers to keep watch from the warmth and comfort of his car. With binoculars trained on the horizon and one eye on data from a GPS tracking system, he will listen attentively for the cacophony of calls that confirm the taiga bean geese are coming home.

Soon the country’s sole and somewhat small flock of taiga bean geese, with their distinctive bright orange coloured legs and matching orange and black beaks, will complete their gruelling flight south and touch down in what is surely a rather unlikely spot.

And for a few months over winter the sparse plateau close to the former mining village of Slamannan, midway between Falkirk and Cumbernauld, will come alive with the coming and going of busy geese families, foraging by day and roosting by peat fields and pools of water by night.

Unlike the tens of thousands of pink-footed geese that are due to descend upon Montrose Basin over the coming weeks, or the massive numbers of barnacle and Greenland white-fronted geese which will soon be spotted overhead on their way to Islay or some other nesting spot, the Slamannan flock is expected to number a mere 250 birds.

It is a shadow of the large numbers which were once dotted around the country. Throughout the 20th century, their numbers dwindled dramatically, partly due to hunting in Sweden and possibly down to climate change..

By 1992, just 18 of the plump, grey geese were recorded wintering in what had been a favourite spot, the Ken/Dee marshes in Dumfriesshire. Some turned up in the Carron Valley, and eventually a handful appeared on the Slamannan plateau.

Birds which once migrated to Scottish moorlands for winter, are now thought to winter in Denmark instead, and the small Slamannan flock is the only one that makes the long journey over the North Sea to UK shores.

“There used to be a flock in Norfolk, but their numbers have virtually disappeared,” says Angus, a retired prison officer who jokes of spending 28 years inside and behind bars but still managing to be outdoors almost all of his spare time.

“Maybe global warming has affected them, we don’t know.”

A bird watcher all his life and a member of the Scottish Ornithological Club for more than half a century, he has been fascinated by the Slamannan geese since first encountering them in the late 1980s.

Since then he has spent countless autumnal hours awaiting their arrival. Once they touch down, he counts them as best he can – he uses a handheld ‘clicker’ to keep track – and logging their movements and behaviour on an online blog.

Regarded as a threatened species, the geese are a conservation priority for Scotland, red-listed and on the Scottish Biodiversity List, making information gathered by Angus and others concerning their migratory movements, stop-over sites in Scandinavia and winter roosting on the plateau even more important.

Angus believes the geese have plumped for Slamannan because the plateau has clear similarities to the quiet spots in Sweden where the birds spend summer.

“Slamannan is in the back of beyond,” he laughs. “We used to joke that if you got in trouble with the police, head for Slamannan because they’ll never find you there.

“There was once a lot of coal mining in the area which served the Carron iron works in Falkirk. The mines closed and the land became agriculture but it’s poor ground and mostly sheep and cattle with one farmer growing some oats.

“If you look around, you could be in Sweden, with its moorland, lochs and forest.

“Most people wouldn’t even know the plateau is there, which is good for the geese.”

Angus initially joined another birdwatcher recording the flock’s movements in 1989, before taking over the task in 2006.

Whereas in the beginning the birds led Angus and others a merry dance as they tried to figure out where they were, modern GPS collars – which look bulky around birds’ necks but which Angus insists do no harm – allow their progress to be tracked.

Having watched them for over 30 years, he is still enthralled by their natural ability to navigate across hundreds of miles to a small patch of moorland in part of central Scotland that’s barely known about it.

“There are two big flocks just now,” he says. “Around 140 in south Sweden around 100 north east of Oslo.

“They will fly across the North Sea and come together as one flock anywhere between Aberdeen and Norwich.

“When they leave depends on what the weather is doing. Last year they landed in Northumberland at 1am, by lunchtime they were in Slamannan.

“The year before, the flocks came together in Norwich. The next day they were in Yorkshire and within a couple of days they were in Slamannan.

“They have a wonderful ability to find their way,” he adds. “When they fly north from England, they seem to fly straight for Edinburgh Airport and then turn left before they end up on Slamannan plateau.

“It’s amazing.”

When winter passes, the birds set off for Sweden via the Firth of Forth, aiming for the Isle of May and then turning east and north on a journey that can take three weeks for them to reach Norway.

“Then the flock splits up, one goes to Norway and the other to southern Sweden,” adds Angus.

The geese then make their way separately to their summer residence, Dalarna County in Sweden.

But even these expert navigators can hit problems. “A couple of years ago as they left the Firth of Forth there was a south easterly gale. One lot of birds were seen flying towards Fair Isle and then landed in Orkney,” says Angus.

“The following day, they turned around and arrived back on the mainland at Caithness. They then flew back to Slamannan via the Cairngorm mountains. They stayed with us for another week or so and then made their second journey to Denmark.”

Now as the nights draw in, Angus is back on patrol, parked up close to where the birds usually flock and waiting for the first sight of their v-formation overhead.

However, despite their low numbers in western Europe, the taiga bean goose is still shot for sport in Sweden.

“It’s sad,” adds Angus. “Bean geese pairs stay together as units all winter. They come here and never leave each other’s sides, they’re always within six feet of each other and the juveniles stay with them too.

“They are really incredible birds.”