However, at the end of this period, seabirds migrate to overwinter mostly in open seas, outside of the Arctic. During this period, which represents a part of the year only, seabirds aggregate in colonies for reproduction where they are more easily accessible. Most of the current knowledge about Hg contamination in Arctic seabirds focused on the breeding period during which Hg was found to spatially vary, with usually higher Hg concentrations in the Canadian Arctic. They are commonly and efficiently used as bio-indicators of the health of their environment. Hence, long-lived top predators like seabirds, found at the end of the food chain usually show some of the highest contamination to Hg. biomagnification process) and accumulates within organisms (e.g. The marine environment is particularly sensitive to Hg, which incorporates the food chain (under is toxic and methylated form – MeHg) in which its concentration increases from one trophic level to the other (e.g. This neurotoxic negatively impacts animals’ health and induces behavioral changes, reproduction issues and in the most extreme case, death. Among them is mercury (Hg), a naturally occurring and non-essential trace element whose emissions increased since the 19th century because of human activities.
Because of their physico-chemical characteristics, pollutants are transported over large distances through atmospheric or oceanic currents. The Arctic, even far from intensive human activities, is contaminated by pollutants emitted at Northern mid-latitudes. Furthermore, Hg concentration in our study was higher than those of the same species of seabirds collected in 1990. The Hg concentration and δ(15)N value were positively correlated across individual birds, suggesting that Hg uptake was linked to the trophic status of consumed prey. Hepatic Hg concentration was high in northern fulmar, whereas Cd level was high in tufted puffin and northern fulmar. As proxies of trophic level and habitat, nitrogen (δ(15)N) and carbon (δ(13)C) stable isotope ratios of breast muscles were also measured. Here, the concentrations of eight heavy metals (Hg, Cd, Cr, Co, Ni, Cu, Zn and Pb) and a metalloid (As) in the liver and kidneys of the northern fulmar (Fulmarus glacialis), thick-billed murre (Uria lomvia), short-tailed shearwater (Puffinus tenuirostris), tufted puffin (Fratercula cirrhata) and horned puffin (Fratercula corniculata) collected in the Bering Sea were measured. It is home to 80% of the seabird population in the USA, 95% of northern fur seals (Callorhinus ursinus), and major populations of Steller sea lions (Eumetopias jubatus), walruses (Odobenus rosmarus) and whales. Contamination by metals in the highly productive offshore region has become a matter of public concern. Seabirds are marine top predators and accumulate high levels of metals and metalloids in their tissues. As parents do not need to check individuality of the chick in the burrow, which they find visually during the day time, the chicks could use all of the acoustic variables to communicate about their nutritional needs. I suppose that such strong change of acoustic variables after food deprivation can be explained by absence of vocal individual identification in these birds. In all studied species, the frequency variables were stronger affected by hunger than the calling rate and call durations.
The effect of food deprivation on most acoustic variables exceeded both the effects of individuality and species. The hungry chicks produced calls higher in fundamental frequency and power variables and at higher calling rate compared to naturally feeding chicks. I found that almost all measured acoustic variables contain information about the chick's state in all studied species. I recorded calls of individual chicks in two conditions: during natural feeding and after experimental four-hour food deprivation. These objects provide an opportunity to study the signalling value of begging calls in the absence of important confounding factors such as nestling competition and predation pressure. Here begging behaviour in three burrow nested, uniparous species of auks (Alcidae) was studied. Fewer researches were dedicated to the temporal-frequency variables of the begging calls themselves and they showed contrary results. However, the majority of the studies have been entirely based on the call counts, and they agreed that vocal activity was a good indicator of chick's nutritional need and/or condition. Begging behaviour is an important element in the parent-offspring conflict it has been studied in many avian species.
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