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OSLO, Sep 5 (Reuters) A small Arctic gull has set a record as the bird most contaminated by two banned industrial pollutants, scientists said.
Eggs of the ivory gull, which has a population of about 14,000 from Siberia to Canada, were found to have the highest known concentrations of PCBs, long used in products such as paints or plastics, and the pesticide DDT.
''Environmental poisons are threatening ivory gulls,'' the Norwegian Polar Institute said yesterday in a statement of eggs collected off northern Norway and Russia. ''Levels of PCB and DDT are higher in ivory gulls than in other Arctic seabirds.'' The long-lasting chemicals, swept north by prevailing winds and currents from industrial centres, often end in the Arctic where they build up in fatty tissues of animals, fish and birds.
A 2001 UN convention outlawed most uses of 12 so-called persistent organic pollutants after the chemicals were found in the breast milk of Inuit women and in polar bears. Levels of many of the ''dirty dozen'' in the Arctic have been falling.
''Ivory gulls are top predators, that's a main reason why they have high levels of contaminants,'' said Hallvard Stroem, of the Polar Institute. The gulls eat cod and other fatty fish and also scavenge dead seals or polar bears for a fat-charged diet.
''We're not sure why the levels are higher than for other birds,'' he told Reuters, adding there were no known local sources of the pollutants to explain the high concentrations.
PCBs, at up to 0.02 per cent of the egg weight, were comparable with those found in some polar bears 20 years ago.
Previous studies show that the chemical pollutants can have effects on birds such as shortening lifespans or thinning of eggshells. Ivory gulls can live about 10 to 20 years.
The shrinking of Arctic sea ice in recent years, apparently because of global warming, also threatens the birds by reducing the size of their habitat. The gulls feed most around the fringes of the ice, where fish and plankton thrive.
''Climate change is an added stress -- the ivory gull is dependent on the sea ice,'' Stroem said.
The survey was carried out after reports that numbers of ivory gulls had plunged by 80 percent in Canada. Stroem said population trends elsewhere were not clear.
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