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Light relief: Oil refinery boon for migrating birds

THEY are loved and loathed in equal measure and would not normally be regarded as beneficial to wildlife.

SHOW ME THE LIGHT: The common redshank is helped to find food by the artificial light at locations such as Grangemouth oil refinery. Main picture: Getty Images
SHOW ME THE LIGHT: The common redshank is helped to find food by the artificial light at locations such as Grangemouth oil refinery. Main picture: Getty Images

But new research has discovered the gas flares and refinery lights that dominate the upper reaches of the Forth estuary are helping some birds survive.

By providing a man-made equivalent for the light of a full moon, the industrial complexes are helping shorebirds stock up on more food during the winter to fuel their arduous spring migrations.

Dr Ross Dwyer and colleagues from Exeter University investigated how artificial light affected the feeding habits of the common redshank in the Firth of Forth, one of Scotland's most industrialised coasts.

As well as major industry such as the Grangemouth oil refinery and Longannet power station, whose lights and gas flares illuminate the intertidal areas at night, the estuary's pristine salt marsh and mudflats are home to hundreds of thousands of migrating birds each winter.

Mr Dwyer measured the amount of artificial light in the Forth at night using satellite images from the US Air Force.

Although previously used to study electrical power consumption, this is the first time such US military data has been used in animal behaviour research.

He then worked out how the light affected the birds' foraging behaviour by attaching tiny radio transmitters to the backs of 20 redshanks.

The devices monitored the birds' location and contained posture sensors to detect how often the birds put their heads down to feed.

Generally, redshanks need to forage day and night during the winter to find enough food to fuel their migrations to Iceland and Scandinavia.

These birds usually forage by sight during the day, which provides them with the most food, and less efficiently at night by locating prey by touch using their bills.

The study, published this week in the British Ecological Society's Journal of Animal Ecology, found artificial light had a major impact on how redshanks searched for food, allowing them to forage more efficiently.

At night, birds in brightly-lit areas foraged for longer and foraged by sight, rather than touch, compared with birds under darker night skies.

Mr Dwyer said: "Artificial light from industrial areas strongly influenced the foraging strategy of our tagged birds.

"It was as if the 24-hour light emitted from lamps and flares on the Grangemouth oil refinery site created, in effect, a perpetual full moon across the local inter-tidal area which the birds seemed to capitalise on by foraging for longer periods at night and switching to a potentially more effective foraging behaviour to locate prey."

The results contrast with other studies, which found adverse effects of light pollution on wildlife. Previous research found artificial light caused newly hatched turtles to head away from the sea, rather than towards it, and caused seabirds such as petrels to collide with lighthouses and other lit structures.

Named for their long bright orange or red legs, the common redshank is a medium-sized shorebird with a greyish brown back and wings in winter, and a black-tipped orange bill.

On their wintering sites, the birds patrol estuaries and coastal lagoons feeding on molluscs, worms and crustaceans. Redshanks are generally wary and nervous birds. Often the first to panic, they give noisy alarm calls, earning them the nickname "sentinel of the marshes".

Redshanks are widely distributed, breeding and wintering across temperate Europe and Asia.

Although numbers are in decline, the species is widespread and quite plentiful in some regions.

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