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My older brother (James Dunson) is a chemical engineer who worked for DuPont in Delaware. In one of his unusual and often humorous stories of the application of chemistry to everyday life I found the following anecdote:
"Jim was a marketing specialist in using iron chloride for wastewater treatment. One of Jim’s
inventions was using traces of organics to help various kinds of treatment (see NJ cinnamon oil below). In
addition to odor, iron chloride can be used to detoxify cyanide in wastewater from gold mining. Gold mines
are often in deserts, and the wastewater ponds are tempting to migrating waterfowl. If cyanide is too high,
ducks check in, but checkout dead. It turns out that synthetic grape flavor = methyl anthranilate is a powerful
repellent for waterfowl. You can sprinkle powdered grape Jolly Ranchers or kool-aid on grass and geese will
not stay. You can dissolve unsweetened grape kool-aid in oil and it will float on cyanide ponds and repel
ducks. That same treated oil can be added with iron chloride according to Jim’s patent, so cyanide is both
treated and ducks repelled. It works for ducks, but for people, please don’t drink the kool-aid!"
The grape flavor that is effective in repelling birds is not very long lasting in nature so various attempts have been made to stabilize it and supply commercial products for repelling for example geese from golf courses (Bird-B- Gone, Bird Shield Repellant Co. and Rejex-it Migrate. In many places Canada geese and other waterfowl can be a huge problem by concentrating on grassy areas around ponds fouling/fowling the grass with their feces which repels human visitors both by the grossness factor and real danger due to pathogenic bacteria. This could be an effective means of moving the geese elsewhere without hurting them. Since birds generally are reputed to be poorly endowed with the senses of smell/taste the discovery of the mechanism of the effect could be quite interesting.
Of course it is rare in nature for anything to be universally true and many of those who feed birds would have found that orioles and some other species are attracted to and eat grape jelly. So the precise nature, origin and purpose of the repellent characteristics of grape flavoring for different types of birds remains elusive and remarkable.
Bill Dunson, Englewood, FL, and Galax, VA