Industrial activities and other drivers of global change, such as ongoing climate warming, increase environmental mercury levels. As mercury enters aquatic ecosystems, microorganisms transform it into its organic and bioavailable form, methylmercury. When biota ingest methylmercury, it can accumulate along the food chain, exposing long-lived top predators, such as some seabird species, to particularly high levels. 

We study the causes and consequences of mercury pollution in the Banter See common terns. Hereto, we collect (i) blood samples from incubating birds (e.g. 1314 samples from 588 birds between 2017 and 2023) using ‘kissing bugs’ specifically bred for this purpose (Becker et al. 2006; see picture), as well as (ii) feather samples from birds that were tracked with geolocators or that died of avian influenza (e.g. 1560 samples from 316 birds between 2017 and 2023) and (iii) samples of food items brought into the breeding colony. These samples are analyzed to quantify mercury contamination levels, in order to investigate (i) effects of migratory behaviour (Bertram et al. 2022), (ii) sex, phenology and within-individual accumulation with age (Bertram et al. 2024a), (iii) genetic disposition (Bertram et al. 2024b), as well as (iv) its transfer across generations and (v) its potential effects on the immune system and long-term fitness consequences.

Causality of the observed patterns is being established with experiments on captive Japanese quail.