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