Bird feathers are a superpower. Small, downy feathers keep birds, and sometimes you, warm during winter. Contour feathers help birds blend in with their surroundings. And interlocking, aerodynamic pennaceous feathers are what allow birds to soar atop air currents and stay dry when diving for fish. But if feathers have a Kryptonite, it turns out to be oil. Oil breaks feathers’ waterproof layer and can leave birds suddenly out in the cold.
This is the mechanism behind new research on the effects of the Deepwater Horizon oil spill, which in April 2010 leaked 200 million gallons of crude oil into the Gulf of Mexico after a drilling rig exploded offshore. With the ten-year anniversary of this disaster just around the corner, findings about its various and immense impacts on wildlife are still trickling in.
The scientists, from several different wildlife research centers and universities, used a “Niche Mapper” model to estimate how much harder the double-crested cormorant, a fish-eating species, would have to work throughout its range to maintain its body temperature after being “oiled” to varying degrees. In the model, birds were either unoiled, or covered in oil once, three times, or six times. Using existing calculations of this species’ energetic expenditure at different times of day and ambient temperatures, the researchers showed that the most heavily oiled birds had to spend, on average, an additional 1.5 hours foraging each day just to make up for lost heat.
In addition to exhausting birds with an extra 1.5-hour foraging shift each day, the model suggests that repeat exposure to oil may threaten cormorants’ success at mating and breeding, or to store enough fat before migrating between winter and summer ranges. These are just a few examples of sublethal effects animals endure from oil exposure, many of which have yet to be evaluated for the dozens of species affected by the Deepwater Horizon spill.