Even light oiling from spills can be catastrophic for birds.

It’s a depressingly familiar sight when an oil well blows or a tanker runs aground: thousands of stranded, helpless animals wallowing in cloying crude oil. ‘Birds are often used as the poster children for the deadly effects of oil’, says Ivan Maggini from Western University, Canada, recalling the shocking images of struggling animals that accompanied the catastrophic Deepwater Horizon oil spill in the Gulf of Mexico in 2010. ‘However, the effects of oiling go far beyond the unfortunate individuals that become heavily oiled’, says Maggini, highlighting the risks of hypothermia and toxin ingestion for lightly oiled birds when they preen. Western University physiological ecologist Chris Guglielmo has been assessing the toxicity of crude oil since 2011. However, no previous study had looked at the effect of oiling on flight, so Maggini, Guglielmo and Karen Dean wondered how even a small amount of contamination might affect the flight of migratory birds that cover great distances.