Mercury concentrations in eggshells of the Southern Ground-Hornbill (Bucorvus leadbeateri) and Wattled Crane (Bugeranus carunculatus) in South Africa

•Total mercury concentrations in hatched eggshells of threatened birds were determined.•Observed Hg levels exceeded those estimated to cause adverse reproductive effects in birds.•Exposure of investigated birds to environmental Hg might be playing some contributory roles to their declining population trends.

In this study, wild hatched eggshells were collected from the nests of threatened Wattled Crane and South Ground-Hornbill in an attempt to determine their total Hg concentrations. A total of fourteen eggshell samples from both bird species were collected from different study areas in the Mpumlanga and KwaZulu-Natal Provinces of South Africa. The eggshells were acid digested under reflux and their total Hg concentrations were determined using cold-vapour atomic absorption spectrophotometry (CV-AAS). The observed total Hg levels for the South Ground-Hornbill samples ranged from 1.31 to 8.88 µg g−1 dry weight (dw), except for one outlier which had an elevated 75.0 µg g−1 dw. The levels obtained for the Wattled Crane samples were relatively high and these ranged from 14.84 to 36.37 µg g−1 dw. Generally, all the measured total Hg concentrations for the Wattled Crane samples exceeded the estimated total Hg levels derived for eggshell which were known to cause adverse reproductive effects in avian species from previous studies. Based on these findings, it is, therefore, possible that the exposure of these birds to elevated Hg may have contributed to their present population decline.