Storm Darcy: Bewick's swans return to Gloucestershire

Bewick's swans return to the Arctic tundra in the early spring to mate, having flown to the UK to avoid a harsher winter

A flock of Bewick's swans which started their migration from the UK to the Arctic last week have returned due to Storm Darcy.

The 20 birds left Gloucestershire's Slimbridge Wetland Centre last week but 11 returned four days later.

Each year Bewick's swans fly 2,485 miles (4,000 km) to the UK to avoid the harsh Russian winter.

But they return to the Arctic in the early spring to breed.

Their journey north at this time of year is triggered by the lengthening days in the UK and they rarely have to abort their journey - which is known as reverse migration.

The swans are identified by the unique yellow and black patterns on their beaks

Kane Brides, a research officer at the Wildfowl and Wetlands Trust (WWT) said it was "very sensible" of the birds to return to avoid the storm's easterly wind direction.

"Arctic migrants like the Bewick's swan are used to chilly weather and, given the extremes of climate they experience, are very adaptable as a result," she said.

"However, freezing conditions reduce food availability and blizzards reduce visibility for migration."

Bewick's swans at the centre are the subject of one of the most intensive wildlife studies in the world and are identified by the unique yellow and black patterns on their beaks.

The study was started by WWT founder Sir Peter Scott and has been running continuously for 50 years.

During that time, it has recorded the lives of almost 10,000 swans.