From heart rate to heat stress: monitoring the direct and indirect effects of climate change and pollutants to Arctic seabirds

Seabirds are considered sentinels of ecosystem health and marine contaminants. Thick-billed murres (Uria lomvia) and black-legged kittiwakes (Rissa tridactyla) have experienced population declines believed to be due to changing oceanographic conditions. For example, over the past 30 years, the diets of murres on Coats Island, Nunavut have shifted from 50% Arctic cod to 50% capelin, a north Atlantic species. To examine whether shifting prey bases could result in an energy deficit, we examined several measures of energetics including heart rate in murres and kittiwakes. Birds with heart rate loggers were injected with doubly-labelled water and deployed with gps-accelerometers to identify which behaviours (flight, swimming, etc.) required the most energy during different stages of the breeding season. Using activity specific metabolic rates, we identified flapping flight as the most energy-costly behaviour in kittiwakes, which is performed mainly during the chick-rearing stage.

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As the Arctic is warming at 4 times the average global rate, increasing air temperatures may also affect birds. Using flow through respirometry, we examined the effects of warming temperatures on several physiological traits associated with heat stress in murres. Murres experienced hyperthermia at low air temperatures relative to heat tolerant (desert) birds and limited ability to dissipate heat, with the lowest evaporative cooling efficiencies ever recorded in birds. Finally, we investigated relationships between perfluoroalkyl acids (PFAAs) and thyroid hormones in murres. Total triiodothyronine (TT3) decreased with long-chain PFAAs in murres. Several long-chain PFAAs were negatively correlated with body mass, an index of body condition. Understanding the impacts of multiple stressors including contaminants may help to predict the overall effects of Arctic climate change on seabirds and other wildlife.