Why is oil so bad for birds’ feathers?

Oil spill incidents always involve birds being rescued and cleaned – but why is oil so damaging, and in many cases fatal, to birds?

Workers help remove oil from the Deepwater Horizon oil spill on a laughing gull at the Mississippi Wildlife Response Center in Gulfport, Mississippi, on West Ship Island in Mississippi on Saturday, July 3, 2010. (James Edward Bates/Biloxi Sun-Herald/MCT)
Oil on a bird's feathers leads to flightlessness © James Edward Bates / Biloxi Sun-Herald / MCT / Getty Images

Oil slicks are lethal traps for seabirds. Oil is thick and sticky. It interferes with the locking mechanism of the feather barbs and displaces the layer of insulating air trapped against the skin, leading to hypothermia, flightlessness and a loss of buoyancy.

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It is also toxic and breaks down very slowly, and afflicted birds ingest it when they try to preen themselves. No surprise then that there’s little hope for a heavily oiled bird.

But even a light oiling can be devastating. Experiments on western sandpipers show that just a thin, invisible film on the wing and tail feathers increases energy consumption in flight by 20%, which can spell disaster for an animal on a tight energy budget.


Do you have a wildlife question you’d like answered? Email your question to wildquestions@immediate.co.uk or post it to Q&A, BBC Wildlife Magazine, Immediate Media Company, Eagle House, Bristol, BS1 4ST.

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Main image: Oil on a bird’s feathers leads to flightlessness. © James Edward Bates/Biloxi Sun-Herald/MCT/Getty