A Taste For Trash

The Glaucous Gull ain’t no gourmet—and that could be bad news for endangered Alaskan birds. A taste for human garbage may fueling an increase in the population of the Arctic’s largest gull, which is also a voracious predator. The trash-based food chain could end up imperiling more than a dozen species, concludes a new study.

Researchers have long known that the Glaucous Gull (Larus hyperboreus) loves to dine out on human garbage. And they strongly suspected that this “anthropogenic subsidy” had played a role in the gull’s dramatic population growth during the 20th century, when some populations doubled in size every 8 years. The landfill link to the gull baby boom, however, had not been rigorously studied.

Two years ago, Emily L. Weiser of the University of Alaska and Abby N. Powell of the U.S. Geological Survey decided to talk trash. In 2008 and 2009, the Fairbanks-based researchers tracked the diets and reproductive success of gulls at 10 breeding colonies in northern Alaska. The colonies were 5 to 75 kilometers away from landfills, and sat in both developed and undeveloped areas. To see what the gulls were eating, the researchers picked through food pellets and leftovers. They also counted how many eggs the gulls laid, and how many chicks survived to fledge.

In some colonies, they found that gulls ate no trash at all. In others, however, up to 85% of pellets and remains had chicken bones, plastic, paper and other signs of landfill cuisine. And all of the samples had evidence that the gulls were eating birds; they found the remains of 30 species, including shorebirds and songbirds. Nearly half of the species are endangered or of “conservation concern.” Finally, statistical analysis showed that fledgling survival was closely linked to garbage consumption, with colonies eating more garbage having higher survival rates.

“Occurrence of garbage in the diet was the second most important factor (after number of eggs per pair),” in fledging rate, the authors conclude in the current issue of The Condor. And as expanding human settlements in the Arctic produce more garbage, “a larger gull population could affect prey species.” One solution, they add, is making landfills less appealing to gulls, perhaps by covering the trash. – David Malakoff

Source: Weiser, E., & Powell, A. (2010). Does Garbage in the Diet Improve Reproductive Output of Glaucous Gulls? The Condor, 112 (3), 530-538 DOI: 10.1525/cond.2010.100020

Image © Frank Wright

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