Large concentrations of glycerin must be used to prevent water from freezing. In order to lower the freezing point to 15 degrees Fahrenheit, for example, you need a 30 percent glycerin solution. Glycerin is a low-level toxin and has a sweet taste. Birds that ingest large amounts of the substance will experience elevated blood sugar levels, causing hyperglycemia and possibly death. And if the birds bathe in the glycerin solution, it may cause their feathers to mat. Birds bathe and preen to enhance the insulation value of their feathers. Matted feathers are poor insulators and can be fatal in cold temperatures.
Float a table-tennis ball in there, or a stick, to stop it freezing as quickly.
..as above, the only bird I can think of fitting that description is a Partridge.