In 2010, a BP oil rig suffered a catastrophic failure. It started spewing oil into the sea, triggering what would become one of the worst environmental disasters in human history. The oil spill made big headlines and drew scorching criticism and ultimately landed BP the largest fine in US history. But oil spills, especially smaller ones, don’t always make the headlines.

Oil kills birds

Oil spills happen more often than you may think, and aside from local media, they rarely get a lot of attention. But these smaller spills can also be very damaging.

Oil pollution can pose a considerable threat, in addition to all the other threats sea birds are already exposed to. The problem stems from how oil interacts with water and with birds’ feathers.

When oil gets spilled into the water, it creates a thin sheen on the water. Lead author Emma Murphy and colleagues from the University College Cork wanted to see how this sheen interacts with feathers and how it affects them.

Feathers play a number of important roles for birds. They provide thermal insulation and keep the birds waterproof — two essential roles for birds making a living at sea. But oil seems to impair these abilities, and previous studies have shown that birds who are exposed to oil are cold, waterlogged, and less buoyant.

Murphy wanted to see how this oil affects individual feathers. She used contour feathers, the feathers that define the body outline, and exposed them to different thicknesses of oil sheen, measuring their resistance to water permeation, the increase in mass, and the clumping of feather barbules.

Ultimately, the researchers conclude that even an extremely thin oil layer 0.1 micrometers thick was enough to significantly affect the feather structure and impact waterproofing.

The silver lining is that the number of oil spills has dropped significantly in recent years, but this means that it doesn’t even have to be a big oil spill — even when the oil is released in smaller amounts, for instance from extraction and transport infrastructure, it can spread across the sea and coat seabirds, affecting them and reducing their chances of survival.

“Chronic small-scale oil pollution is commonly overlooked in the marine environment, though it has been shown to have serious implications for the fitness and survival of seabirds. This study examined one species, but the results can be extended to other species that rely on waterproofing to stay healthy when at sea for long periods,” Murphy said.

The study was published in Royal Society Open Science.