Morphometric parameters and total mercury in eggs of snowy egret (Egretta thula) from Cartagena Bay and Totumo Marsh, north of Colombia

► Egret eggs from polluted and non-polluted sites were analyzed for total Hg. ► Eggs from Cartagena Bay have greater total Hg levels than those from Totumo Marsh. ► Eggshell thickness is lower for egret eggs from the bay when compared to the marsh. ► T-Hg in egg content negatively correlated with eggshell thickness in the less polluted site.