Even traces of oil on bird feathers affects flight

After devastating oil spills like the 2010 Deepwater Horizon disaster in the Gulf of Mexico, the impact on birds is easy to see when they lay dead on the ground covered in thick, murky oil.

But researchers wanted to find out what happens to the birds that don’t die. How are the ones with smaller traces of oil affected by these spills?

“When we were working on the Deepwater Horizon Natural Damage Assessment for the U.S. Fish and Wildlife Service, the first thing you can see is the dead birds completely covered in oil, and it’s quite easy to quantify the amount of birds that actually died because of that,” said Ivan Maggini, the lead author of a recent study on the birds. “But what is far less easy to quantify is the many birds that don’t die, or they die later because of toxic effects.”

In a study published in the Journal of Experimental Biology, Maggini and his colleagues studied how the western sandpiper (Calidris mauri), a migratory shorebird, is affected by small amounts of oil collected from the Deepwater Horizon spill.

The team caught the birds with nets on the coast of Vancouver, one of the main stopover sites for the birds. “We had to actually catch the birds that were on migration because those were the ones that were motivated to fly,” said Maggini, who worked on the study as a postdoctoral researcher at Western University in Ontario.

After catching the birds, the researchers put a small amount of oil on the birds’ wings and tails to replicate birds with a trace amount of oil from an oil spill. About a week later, the team placed oil on the wings, tails and belly of the same birds, representing lightly-oiled birds.

Maggini and his colleagues then had the birds fly through a wind tunnel to see how they would fare. In order to determine how the birds’ flights were affected, the team measured how much energy they used by determining how much fat they had before and after their flights. Less fat meant they were using more energy to fly.

For birds with oil only on their wings and tails, their flight cost was increased by about 20 percent. Those with more oil increased their flight cost by 45 percent. “It was striking,” Maggini said.

This may mean that when the birds make stopovers to replenish their energy they will need more time to recuperate, he said, causing them to lose time during their flight and miss out on reproduction down the line.

“The effects of oil spills are way more extensive than what we see by just looking at carcasses on the shore,” Maggini said. “Hopefully, people will pay more attention to something that adds to what we already know about the effects of oiling, and I hope the attention toward this problem gets stronger.”

Header Image: A western sandpiper stands along the shore in Nome, Alaska. The birds make extensive migratory journeys that can be affected when small amounts of oil impact their flight ability. ©Mick Thompson