U.S. Department of Agriculture: Animal and Plant Health Inspection Service


Date of this Version



Chicago Department of Environment (March 18, 2012) 30 pages


The large ring-billed gull (Larus delawarensis) population in Chicago has caused various conflicts including general nuisance, property damage, economic losses, and threats to human health and safety. Several studies have linked ring-billed gulls to increased levels of fecal indicator bacteria such as Escherichia coli (E. coli) in nearshore waters. Results of tests for E. coli have led to the issuance of swim advisories and swim bans for Chicago beaches.

The objectives of the 2011 Chicago Ring-billed Gull Damage Management Project were to (1) reduce the local production of ring-billed gulls, (2) reduce the severity of conflicts with gulls including the issuance of swim advisories and swim bans, (3) evaluate how limiting the production of gulls affects gull use of Chicago’s beaches, and (4) educate the public regarding the link between gulls and swim advisories and swim bans. The Chicago Department of Environment, with support from the Chicago Park District, requested that USDA-APHIS-Wildlife Services (USDA-WS) provide assistance for the fifth consecutive year to implement this project.

During the pilot project in 2007, USDA-WS established that oiling eggs with food-grade corn oil was a successful method in reducing gull production. During the initial year, 52% of the nests were rendered inviable. From 2008 – 2010, oiling 80%, 81%, and 75% of the nests was found to make a significant additional reduction in the number of hatch-year gulls using Chicago beaches compared to 2007. The goal of treating 80% of the available nests was established again for the previously treated colonies in 2011. The incorporation of an aerial survey in 2011 furthered our ability to minimize the production of ring-billed gull young in Chicago by identifying locations of additional nesting colonies.

Fewer hatch year gulls used Chicago’s beaches following egg oiling and there was a reduction of total gulls by 44% when compared to 2007. During the timeframe of these successful reductions of gull production, the number of conflicts caused by gulls (including the frequency of swim advisories and swim bans) were also decreasing. Water quality data were available from the Chicago Park District during our five treatment years and the prior year (pretreatment year) for 18 beaches. Canine harassment did not occur on 15 of the 18 beaches studies.

To further reduce the number of gulls using Chicago’s beaches, an education program was implemented in 2011 to inform beachgoers on the importance of not littering and not feeding the birds. The objective of the program was to improve beach health by reducing the availability of anthropogenic food sources which are a major attractant to gulls. Over 4300 people were surveyed and deeply educated about beach health issues and 4,171 (96% of those surveyed) beachgoers agreed to pledge to keep Chicago beaches healthy by not littering and not feeding the birds. Thousands more were exposed to information about the connections between birds and water quality through the aggressive placement of posters at the beaches which discouraged hand-feeding of birds and littering.

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