The great arrival: Britain's winter swans and geese and their long journeys south

The days are shortening across Britain, and high above its estuaries, marshes and flooded washes one of the natural world's great annual dramas is quietly unfolding once again. As temperatures fall in the far north, tens of thousands of swans and geese are pouring in from Iceland, Greenland and Arctic Russia to spend the colder months on these comparatively mild and food-rich islands.

For many people it is the sound as much as the sight that marks the change of season. The wild bugling of swans passing overhead at dusk, or the clamour of a goose skein strung out against a grey sky, has signalled the coming of winter for countless generations. Today those same journeys are watched, counted and cherished at a string of wetland reserves scattered the length of the country.

A journey measured in thousands of miles

What makes these arrivals so remarkable is the sheer scale of the effort behind them. According to the Wildfowl and Wetlands Trust, the conservation charity known as WWT, the pink-footed geese that reach reserves such as Martin Mere in Lancashire breed in Iceland and eastern Greenland, where they raise their young during the short Arctic summer before heading south when the light and the food begin to fade.

The trust says these geese can travel over eight hundred miles to reach their British wintering grounds, flying at around thirty miles an hour and taking two to three days to complete the crossing. It is an exhausting feat of endurance for a bird, and one repeated by whole families together, with young birds learning the route by following their parents south for the very first time.

The pink-footed geese of Martin Mere

Few places capture the spectacle better than WWT Martin Mere, where the trust reports that as many as forty thousand pink-footed geese may gather at once during the peak of the season. At dawn and dusk the birds lift off or drop in to roost in vast, noisy clouds, a sight that draws visitors from across the region and has become one of the highlights of the reserve's calendar.

The scale is not merely local. WWT notes that a very large share of the entire world population of pink-footed geese spends the winter in Britain, which places a particular responsibility on the wetlands that host them. To celebrate the return of the flocks, Martin Mere launched a dedicated autumn event called Goosefest, running from early September to mark the moment the geese begin streaming back in earnest.

The return of the whooper swans

Arriving alongside the geese are the whooper swans, another iconic migratory visitor that flies in from Iceland to escape the harsh northern winter. Larger and wilder in character than the resident mute swans of park lakes, they are easily recognised by their bright white plumage and their distinctive yellow and black bills, and by the loud, haunting calls that give the species its name.

The timing of their return is watched closely each year. At Martin Mere the first significant influx last autumn came in early October, when more than a hundred birds were counted in a single day, followed by a dawn survey that logged well over a hundred swans spread across the reserve. Each arrival is logged as part of a long tradition of monitoring that stretches back many decades at Britain's wetland centres.

Bewick's swans and a worrying decline

Not every winter visitor is thriving, however. The Bewick's swan, the smallest of the swans that reach Britain, makes an even longer journey than the whooper, travelling from breeding grounds in Arctic Russia and staging through wetlands in Estonia, Latvia, Germany and the Netherlands before finally reaching sites such as the Ouse Washes in East Anglia, an internationally important refuge for the species.

Conservationists have grown increasingly concerned about these birds. WWT and the British Trust for Ornithology report that the north-west European population of Bewick's swan fell by around thirty-eight per cent between 1995 and 2010, and the species is now listed as endangered on the European Red List. In recent winters the numbers reaching Britain have struggled to climb back to the levels seen in earlier decades.

Milder winters and the puzzle of short stopping

Part of the explanation appears to lie in a warming climate. As winters become milder along the birds' flyway, many Bewick's swans no longer need to fly the full distance to Britain and instead settle in countries further east, a behaviour that researchers describe as short stopping. Whooper swans have so far coped better, but the contrast between the two species has become a subject of close scientific study.

The pattern is a reminder that these migrations are not fixed and timeless, but sensitive to changes far beyond Britain's shores. What arrives on a Norfolk washland or a Lancashire mere in any given autumn is shaped by conditions across a whole continent, from Arctic breeding success to the weather over the North Sea, which is why the careful counting carried out at reserves matters so much.

Where to witness the spectacle

For anyone wishing to see the great arrival for themselves, the coming weeks offer some of the finest wildlife watching of the year. WWT reserves such as Martin Mere, Slimbridge on the Severn and Welney on the Ouse Washes lay on floodlit swan feeds and goose gatherings through the winter, and there is no admission needed to hear the wild music of the flocks passing overhead at dusk across much of the country.