Abstract
Canada geese (Branta canadensis) populations are a modern conservation success story. Protection under the Migratory Bird Treaty Act, carefully managed hunting, protection of habitat, and acclimation to human activities have allowed this species to flourish. It is the acclimation to human activities that pose problems to zoo patrons, grounds, and animals across the United States. Indeed, many state conservation organizations now have to address some of these bird populations as nuisance animals. At the Kansas City Zoo, as elsewhere, the aggressive nature of geese looking for food and defending territories have injured several people. Droppings pose a significant risk to zoo patrons and animals.
At the Kansas City Zoo, methods to deter geese have met with little success. The birds are federally protected from disturbance by humans. Few, if any predators exist at the zoo that can negate overpopulation. The Missouri Department of Conservation (MDC) removes nests and eggs from an estimated 500 Canada geese each year on zoo grounds.
Euthanasia has been suggested as part of a nuisance animal permit but is not supported by a majority of people. The combination of a lack of predators, ample food supply, and nesting sites continues to build populations of geese at the zoo. Geese destroy grass in the African Plains exhibit each year, pose risks of fouling waterways, and injure several people each year.
In light of these problems, the Kansas City Zoo launched an initial study to evaluate the effectiveness of an ingested deterrent, 9,10 anthraquinone (Flight Control, EBI Environmental Biocontrol, Intl., Wilmington, DE, USA). Flight control contains 50% 9,10 anthraquinone and 50% inert ingredients. The product is diluted with water at the rate of 2 quarts with 50 gallons of water. The product is sprayed on dry, grassy areas, where geese frequent. The product contains an ultraviolet dye that avian species can readily detect. In feeding trials, birds eating affected grass or grain become nauseated and subsequently avoid the area.1-4 Avian species are subsequently conditioned to avoid areas where the dye is visually detected.
During the summer of 1999, three test plot areas were measured and flagged to monitor goose activity. All three areas were selected based on high density, daily geese activity in areas that were integral to public viewing of zoo animals. A one-time topical application of the diluted product was applied to all three areas by the MDC. Observations from zoo staff were made over the course of the following 10 days. All staff reported decreased to nonexistent usage of all three areas by Canada geese. In one case, peripheral geese were herded towards the flagged areas. The geese avoided entering the treated areas at all costs, circumventing an area next to a farm-pond exhibit on zoo grounds. Several geese were observed to “star-gaze” for several minutes at a time. No fatalities were observed, and no geese could be caught to evaluate clinical illness. A second study will be evaluated over the spring and summer of 2000 to determine cost effectiveness and long-term efficacy of this product in a zoological institution.
Potential advantages with this product are training geese to avoid zoo exhibits, public restaurants, playground areas, and public pathways without causing injury or harm to the geese. Disadvantages are weekly reapplication, expense, and manpower.
Use of this product may allow zoological institutions an alternative means to quietly dissuade Canada geese from zoo grounds.
Literature Cited
1. Avery, M.L., J.S. Humphrey, and D.G. Decker. 1997. Feeding deterrence of anthraquinone, anthracene, and anthrone to rice-eating birds. J Wildl Manage. 61:1359–1365.
2. Avery, M.L., J.S. Humphrey, and E.A. Tillman. 1998. Responses of blackbirds to aerial application of flight control bird repellent to ratoon rice in Cameron Parish, Louisiana. USDA, National Wildlife Research Center, Gainesville, FL.
3. Blackwell, B.F., D.A. Helon, and R.A. Dolbeer. 1999. Repelling sandhill cranes from corn: whole-kernel experiments with captive birds. USDA/Aphis Wildlife Services. Interim Report to the International Crane Foundation.
4. Dolbeer, R.A., T.W., Seamans, B.F. Blackwell, and J.L. Belant. 1998. Anthraquinone formulation (Flight Control™) shows promise as avian feeding repellent. J Wildl Manag. 62(4):1558–1564.