Interestingly, this just came up on BirdChat -- about Ivory Gull decline. I wonder if any gull species are being affected, but have higher population levels so that (as yet) declines have not been so obvious.
Gail Mackiernan
Colesville, MD
-------------- Forwarded Message: --------------
From: Jean Iron <>
To:
Subject: [BIRDCHAT] Mercury could cause ivory gull's decline
Date: Mon, 26 Feb 2007 19:58:10 +0000
> This story is from Nunatsiaq News in Iqaluit, Nunavut Territory,
> Canada. We thank Mark Pimlott of Igloolik for bringing this important
> information about Ivory Gulls to our attention.
>
> Jean Iron & Ron Pittaway
> Toronto ON
>
> Nunatsiaq News, Friday February 23, 2007
>
> Mercury Could Cause Ivory Gull's Decline
>
> By John Thompson
>
> The ivory gull has more mercury in its eggs than any other seabird in
> the Arctic, researchers have found, a fact that could explain why
> numbers of the boisterous seabird have plummeted dramatically over
> the last 20 years. Population counts done during the early 1980s
> found about 2,400 birds, while a survey done from 2002 to 2006 by
> Canadian Wildlife Services only found several hundred birds, a drop
> of 80 per cent. This decline prompted the Committee on the Status of
> Endangered Wildlife in Canada to assess the ivory gull as an
> endangered species last year.
>
> Climate change and excessive hunting in Greenland are both possible
> reasons why the ivory gull's populations have nose-dived. But another
> possibility has been discovered by Birgit Braune, a research
> scientist with Environment Canada who studies toxic chemicals in
> Arctic wildlife, specializing in seabirds. She examined ivory gull
> eggs collected from Seymour Island, a tiny island just north of
> Bathurst Island, in 1976, 1987 and 2004, using the tissue bank at the
> National Wildlife Research Centre in Ottawa, and ran a series of
> tests to look for persistant organic pollutants, such as PCBs and
> DDT, as well as flame retardants.
>
> Most tests bore no surprises. But when she tested for mercury, a
> heavy metal that interferes with the nervous systems of animals, she
> found "the highest mercury levels in eggs of seabirds in the
> Arctic." "That certainly was an attention getter," she said during
> an interview last week. Some eggs contained enough mercury to prevent
> other birds from reproducing, although whether this would hold for
> ivory gulls is not yet clear. High mercury levels could also affect
> the behavior of birds, during the crucial period when a chick needs
> to be fed and kept warm. But just how high mercury levels affect the
> ivory gull is unknown, she stresses. Some animals, particularly
> marine mammals, are able to cope with high mercury levels because
> their bodies contain another chemical, called selenium, which
> combines with mercury and renders it harmless. "The bottom line is,
> it's high. We don't know what that means," she said of the test
> results. "To me, it's one piece of the puzzle." Braun suspects the
> high mercury levels are the result of the ivory gull's metabolism,
> which is higher than other gulls in the Arctic. "It means it needs to
> eat more, and by default, it needs to take in more mercury," she
> said. And because the bird is a scavenger, it eats at the top of the
> food chain, where chemicals such as mercury accumulate.
>
> Researchers already know mercury levels aren't preventing ivory gulls
> from laying eggs, says Mark Mallory, who helped conduct the CWS
> survey of ivory gull populations. During the summer surveys,
> researchers saw healthy clutches of eggs in the birds' nests. So the
> next step will be to study ivory gulls in the wild during the summer
> nesting months, to see whether they behave irratically with their
> young chicks, Mallory says. As of yet, there are no plans to do this.
> But this summer CWS researchers will study another factor that could
> affect ivory gulls: traffic to and from the Diamondex mineral
> exploration site, west of Arctic Bay. Arctic Bay residents have
> expressed concern that helicopter traffic to the site may scare
> wildlife. So this year, CWS researchers, with the cooperation of
> Diamondex staff, will study how the nearby population of ivory gulls
> on Brodeur Peninsula react to air traffic. But first they will need
> to find ivory gulls. During the 1980s, researchers counted between
> 500 to 700 birds on the Brodeur Peninsula, which is an area about the
> size of Prince Edward Island.
>
> But "last year, we saw one gull," Mallory said last week. "One year
> we saw no gulls." "We were probably missing a few birds, but most
> seabirds do return to the same spots," he said. That could be
> explained by late snowfall, which may have encouraged the birds to
> simply skip nesting that year. There is some good news from the CWS
> survey of ivory gulls: researchers discovered an unknown colony last
> summer on eastern Ellesmere Island of about 600 birds. "That was a
> really big coup for us," Mallory said. "That represents the main
> heart of the breeding range in Canada." Evidence suggests this colony
> is permanent, and not merely ivory gulls who relocated from a
> previously known location. That's because new nesting grounds are
> usually barren, without much vegetation, while permanent nesting
> grounds are distinguished by bright orange lichen, sedges and other
> vegetation, fertilized by the birds' guano. The bad news: there's
> every reason to believe declines have occured everywhere else in the country.
>
> Other than mercury, researchers have a few other theories why the
> ivory gull's population has declined so abruptly. One is that an
> unsustainable number of gulls were hunted in Greenland during the
> 1980s, where migratory seabirds are eaten more often. The ivory gull
> isn't actively hunted in Nunavut, although some hunters have
> expressed affection towards the bird for its brash behavior. It's
> been known to swoop in after a polar bear or whale kill to plunder
> some of the fat, right in front of a hunter's eyes. Global warming
> could also play a role. Ivory gulls nest on top of narrow peaks
> surrounded by glaciers, and spend their winters floating through the
> icy waters of Davis Strait on multi-year sea ice. Shrinking ice
> levels could threaten this habitat.
> ______________________________________
> Jean Iron and Ron Pittaway
> OFO News Editors
> Ontario Field Ornithologists
> 9 Lichen Place
> Toronto ON M3A 1X3
> 416-445-9297
> www.ofo.ca
>
>
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