November 08, 2010
"Gulls will eat just about anything: french fries, remains of a bowhead whale harvested by villagers, or live shorebird chicks and lemmings," said study coauthor Abby Powell of the U.S. Geological Survey's Alaska Cooperative Fish and Wildlife Research Unit in an e-mail interview with mongabay.com. Glaucous gulls eat the young of many birds like phalaropes, Dunlin, plover, dowitchers, and sandpipers, said Powell, who published the study with lead author Emily Weiser of the University of Alaska, Fairbanks.
Glaucous gulls in northern Alaska raid an open dumpster for an easy meal. Credit: Emily Weiser/University of Alaska, Fairbanks
Glaucous gulls look like most other seagulls. Birders in coastal Alaska, Washington, and Oregon identify them by their "glaucous," or bluish-gray, backs and wings. Like other gulls, they make an opportunistic living swiping meals of fish, crustaceans, baby birds, small mammals, and garbage.
Researchers picked through regurgitated pellets and food remains around the nests of Glaucous gulls in ten breeding colonies during 2008 and 2009 to see how the gulls were exploiting trash from human settlements along Alaska's coast. Colonies varied in size from 7 to 23 nests. Some colonies were in pristine areas with no garbage, some were near human developments with open landfills, and some were near settlements where people incinerated their garbage.
The scientists found that gulls in colonies closest to open landfills consumed two to three times more garbage than gulls in undeveloped areas or in areas where trash was incinerated.
They also found that gulls that ate the most garbage hatched the most chicks. In each colony, the teams counted how many nests the birds established during each breeding season. They returned two months later to count newly hatched chicks. The gulls in regions with landfills averaged 1.75 chicks per breeding couple, while the gulls with no access to trash averaged only 0.5 chicks per couple. Gulls in regions where trash was incinerated had more babies than gulls eating only natural foods, but they still couldn’t outcompete their trash-eating counterparts.
Their findings resemble those of a similar study conducted on California gulls in San Francisco Bay. "We found that California gull movements are highly influenced by local landfill locations," said Josh Ackerman, research wildlife biologist with the U.S. Geological Survey's Western Ecological Research Center in an email interview with mongabay.com. "Breeding waterbirds nesting in wetlands adjacent to these landfills have elevated predation rates, especially on chicks."
Gull populations could explode as Alaska opens more areas for oil exploration and people begin to settle in formerly pristine coastal areas. According to Powell, incinerating trash and covering dumpsters may be an important tool for keeping this insatiable predator under control as humans move in.
CITATION: Emily Weiser and Abby Powell. Does garbage in the diet improve reproductive output of glaucous gulls? Condor. August 2011. doi: 10.1525/cond.2010.100020
Donna Hesterman is a graduate student in the Science Communication Program at the University of California, Santa Cruz.