Dietary mercury exposure causes decreased escape takeoff flight performance and increased molt rate in European starlings (Sturnus vulgaris)

Abstract

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.

Evidence of negative seasonal carry‐over effects of breeding ground mercury exposure on survival of migratory songbirds

“…Methylmercury has been demonstrated to impair bird immune function (Hawley et al 2009, Lewis et al 2013), foraging behavior (Kobiela et al 2015), navigation (Moye et al 2016), and flight ability (Carlson et al 2014, Ma et al 2018, which could be particularly detrimental during long-distance migration. In this study, we used songbird feathers grown prior to autumn migration to examine the link between Hg exposure at breeding grounds and songbird survival until the subsequent spring return migration (a seasonal carry-over effect).…”

Short-term mercury exposure disrupts muscular and hepatic lipid metabolism in a migrant songbird

“…Additional impacts to flight endurance and refueling ability could result from effects of MeHg on the expression and function of other critical proteins like hormone-sensitive lipase, lipoprotein lipase, long chain acyl-CoA synthetase, albumin, malic enzyme, fatty acid synthase, and hemoglobin 9 , 23 , 63 , 73 , 75 . There is also the potential for mercury’s neurotoxicity to affect flight biomechanics, as observed in our birds 17 , which could further weaken endurance through reduced flight efficiency 9 , 17 , 76 . Much remains to be learned about the effects of MeHg on the physiological systems and processes that give migratory birds the remarkable ability to biannually fly thousands of kilometers between breeding and wintering grounds.…”

Heavy metal accumulation as a threat to the endangered Egyptian vulture(Neophronpercnopterus L.) in Turkey

“…These values are below the threat level (Table ). It has been reported that the sublethal effects of Hg on the breeding success and flight efficiency of birds occur at 5-40 μg g −1 d.w. (Burger and Gochfeld, 1997;Carlson et al, 2014;Varian-Ramos et al, 2014).…”