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A study of migratory hoverflies on a North Sea oil rig has revealed their vital role as long-distance pollen transporters.

Researchers studied 121 marmalade hoverflies that landed on an oil rig in the Britannia oil field, 200 km off the coast of Scotland.

Pollen was found on 92% of the hoverflies and—with no vegetation on the rig, and no land nearby—this shows they can transport pollen over great distances, potentially linking plant populations that are hundreds of kilometers apart.

The hoverflies carried pollen from up to 14 different plant species, including many common crops—highlighting their important role in agriculture.

The study was led by the University of Exeter. The paper, published in the Journal of Animal Ecology, is titled "Long range pollen transport across the North Sea: Insights from migratory hoverflies landing on a remote oil rig."

"By analyzing the pollen samples and wind patterns, we estimate that many of the hoverflies had flown from places including the Netherlands, northern Germany and Denmark—over 500km away," said Toby Doyle, from the Center for Ecology and Conservation on Exeter's Penryn Campus in Cornwall.

"The most common pollen types were common nettle, black elder and meadowsweet—but they also carried pollen from crops including vegetable, legume, cereal, nut and fruit species."

Dr. Eva Jimenez-Guri, also from the Center for Ecology and Conservation, added, "By flying all over Europe—from northern islands and Norway to Spain and Portugal—these migratory hoverflies are probably providing a range of vital benefits both to humans and to plant biodiversity.

"As well as being beneficial pollinators, marmalade hoverflies are also natural pest controllers—eating prey including aphids, helping to reduce crop damage."

The hoverflies in the study landed on the oil rig in June (probably during northward migrations) and July (when migrations are mostly to the south).

Preferring to fly with the wind, the hoverflies wait for wind to blow in their desired migratory direction before taking off.

They probably landed on the oil rig to rest, or in the hope of finding food.

Dr. Karl Wotton added, "The results highlight the important role of migratory hoverflies in long-distance gene flow. The next stages of investigation should look at the ecological and agricultural implications of this phenomenon at the continental scales at which these species move."