Meeting Abstract
Many songbirds migrate long distances and may be exposed to different dietary methyl-mercury (MeHg) concentrations during their annual cycle. There is ample evidence that environmental MeHg exposure can cause reductions in avian fitness, particularly in aquatic species during breeding. However, recent work indicates that terrestrial songbirds that live in association with MeHg contaminated environments can bioaccumulate significant MeHg in tissues. How the MeHg levels we observe in migratory songbirds affect flight performance and migration is still unknown. We conducted a MeHg dosing experiment (0.5ppm in wet weight, relevant to contaminated environment) with yellow-rumped warblers (Setophaga coronata) while they were in a hyperphagic, migratory state. Warblers rapidly bioaccumulated dietary meHg to 10 to 20 fold in blood, approximately 60 fold in liver, 40 fold in brain and muscle, and over 100 fold in kidneys over after 2 weeks. There was no significant effect of MeHg on vertical takeoff ability. In 2-hour wind tunnel flights, MeHg treated warblers had a significantly greater median of numbers of strikes (landing or losing control), longer strike duration, and shorter flight duration than control birds. There was also a positive correlation between total blood Hg concentration and the median of strikes in the MeHg treated warblers. In terms of energetics MeHg treated warblers had a nearly significant greater cost of transport (2-tailed P = 0.065), which may have been caused by their poorer control in flight. In conclusion, hyperphagic migratory birds rapidly accumulate MeHg from the diet, which has the potential to affect flight performance and migration ability.
