Meeting Abstract
The fate of birds that become oiled during oil spills such as the 2010 Deepwater Horizon (DWH) spill in the Gulf of Mexico is an important aspect of assessing environmental impacts. Dead birds can be counted, but understanding the fitness costs of exposure to small amounts of crude oil that are not lethal is difficult and often ignored. We studied the effects of DWH oil applied to wing, tail and body feathers on the flight of the Western Sandpiper (Calidris mauri). Flight energetics and biomechanics were measured using quantitative magnetic resonance analysis, high-speed video, and accelerometry. Takeoff speed was reduced by over 30 %, and takeoff angle was reduced in trace-oiled birds compared to controls. Oiled birds would require twice the time to reach cruising speed, and fly lower to the ground, potentially making them more vulnerable to aerial predators. Wind tunnel flights showed that trace/moderate oiling increased flight energy costs by up to 41 % relative to controls. Oiled birds also had decreased flight ability and decreased voluntary duration of flight. The flight power curve, as indicated by wingbeat frequencies at different flight speeds, was altered in moderately oiled birds. Oiling resulted in faster wingbeat frequencies, and there was an increase in wingbeat amplitude at low speeds in trace and moderately oiled birds. Thus, migration would be slower and/or more costly for an oiled bird. Our results suggest that trace to moderate amounts of crude oil (oiling categories widely observed in live resident and migratory birds in the aftermath of the DWH spill) negatively affect the aerodynamic properties of feathers, substantially reducing takeoff and endurance flight performance with associated fitness costs.
