Dietary mercury exposure causes decreased escape takeoff flight performance and increased molt rate in European starlings (Sturnus vulgaris)
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Mercury is a widespread and persistent environmental contaminant that occurs in aquatic and terrestrial habitats. Recently, songbirds that forage from primarily terrestrial sources have shown evidence of bioaccumulation of mercury, but little research has assessed the effects of mercury on their health and fitness. There are many indications that mercury negatively affects neurological functioning, bioenergetics, and behavior through a variety of mechanisms and in a wide array of avian taxa. Effective flight is crucial to avian fitness and feather molt is an energetically expensive life history trait. Therefore, we investigated whether mercury exposure influenced flight performance and molt in a common songbird, the European starling (Sturnus vulgaris). Specifically, we dosed the diet of captive starlings with methylmercury cysteine at 0.0, 0.75, or 1.5 μg/g wet weight and recorded changes in flight performance after 1 year of dietary mercury exposure. We also recorded the annual molt of wing feathers. We found that individuals dosed with mercury exhibited decreased escape takeoff flight performance compared with controls and blood mercury was also correlated with an increased rate of molt, which can reduce flight performance and thermoregulatory ability. This study reveals two novel endpoints, flight performance and molt, that may be affected by dietary mercury exposure. These findings suggest a potential impact on wild songbirds exposed to mercury levels comparable to the high dosage levels in the present study. Any decrease in flight efficiency could reduce fitness due to a direct impact on survival during predation events or by decreased efficiency in other critical activities (such as foraging or migration) that require efficient flight.
KeywordsFlight Mercury Molt Sub-lethal effects European starling
This study was funded by E.I. DuPont de Nemours and Company and research was completed with oversight from the South River Science Team, which is a collaboration of state and federal agencies, academic institutions, and environmental interests. This study was also supported by NSF award IOS-1257590. The College of William and Mary provided additional funds. Thank you to Margaret Whitney for dose preparation and analyses. Special thanks S. Laurie Sanderson for advice and to all the graduate and undergraduate researchers who assisted in developing and carrying out this project.
Conflict of interest
The authors declare that they have no conflict of interest.
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