Behaviour 2019
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Is mercury affecting the ability of Arctic seabirds to respond to changes in ice availability?
Ilse Esparza 1, Kim J. Fernie2, Emily S. Choy 1, Kyle Elliott1. 1McGill University , Ste Anne de Bellevue, Quebec , Canada; 2Environment and Climate Change Canada, Burlington , Ontario , Canada

Arctic species are facing multiple stressors from climate change and contaminants, especially mercury which occurs at high levels in Arctic wildlife. We investigated whether mercury increases the impact of climate change on the thick-billed murre (Uria lomvia) by limiting its ability to respond to extreme changes in ice availability. We studied the thick-billed murres near their southern range limit during tree breeding seasons under early-ice (2017), moderate-ice (2016) and late-ice (2018) conditions. We tracked 163 breeding adults using GPS-accelerometers to classify their behaviours (i.e. total time at the colony, diving, swimming & flying) and measured concentrations of hormones (T3, T4 & corticosterone) and mercury. Under poorer ice conditions (2016, 2017), T3, which regulates oxygen consumption, was negatively associated with diving. In those same years, mercury was positively (moderate-ice) and negatively (early-ice) related to T3. Mercury may influence the ability of thick-billed murres to adjust their foraging behaviours to variation in ice cover, especially during years where ice-break up occurs earlier, demonstrating how climate change and contaminants can interact.